Publications Supported by the Blake-Nuttall Fund
xArnold, J.M., I.C.T. Nisbet, and R. Veit. 2011. Assessing aural and visual curing as tools for seabird management. Journal of Wildlife Management. 75:495-500.
Abstract: Social attraction, that is, mimicking of active and productive colonies via audio playback of calls of breeding conspecifics and the use of decoys, is commonly used to attract birds to newly established or restored breeding sites. However, little is known about the relative importance of aural versus visual cues for identify nesting areas. Such information is important for design and evaluation of management protocols. We studied the effectiveness of decoys (visual cues) and playbacks (audio cues) as methods for restoring a colony of common terns (Sterna hirundo) at Muskeget Island, Massachusetts, USA. We used a 2-year, crossover experiment with 3 treatment areas: audio and visual, audio only, and visual only. We reversed treatment areas in the second year to control for previous nesting area or substrate preference. In both years, nests were built 9-101 m downwind of loudspeakers. There was no overlap in areas used for nesting between years and no nests were built within decoy plots in either year. Behavioral observations showed that birds responded to decoys only when within range of sound treatments. Conspecific vocalizations appear to be important proximate cues for seabird colony site selection and should be given priority in management protocols using social attraction.
Balakrishnan, C.N., and S.V. Edwards. 2009. Nucleotide variation, linkage disequilibrium and founder-facilitated speciation in wild populations of the zebra finch (Taeniopygia guttata). Genetics 181:645-660.
Abstract: The zebra finch has long been an important model system for the study of vocal learning, vocal production, and behavior. With the imminent sequencing of its genome, the zebra finch is now poised to become a model system for population genetics. Using a panel of 30 noncoding loci, we characterized patterns of polymorphism and divergence among wild zebra finch populations. Continental Australian populations displayed little population structure, exceptionally high levels of nucleotide diversity (pi = 0.010), a rapid decay of linkage disequilibrium (LD), and a high population recombination rate (rho approximate to 0.05), all of which suggest an open and fluid genomic background that could facilitate adaptive variation. By contrast, Substantial divergence between the Australian and Lesser Sunda Island populations (K(ST) = 0.193), reduced genetic diversity (pi = 0.002), and higher levels of LD in the island Population suggest a strong but relatively recent founder event, which may have contributed to speciation between these populations as envisioned under founder-effect speciation models. Consistent with this hypothesis, we find that tinder a simple quantitative genetic model both drift and selection could have contributed to the observed divergence in six quantitative traits. In both Australian and Lesser Sundas populations, diversity in Z-linked loci was significantly lower than in autosomal loci. Our analysis provides a quantitative framework for studying the role of selection and drift in shaping patterns of molecular evolution in the zebra finch genome.
Barnett, J.M., and D.R.C. Buzzetti. 2014. A new species of Chichlocolaptes Reichenbach 1853 (Furnariidae), the ‘gritador-do-nordeste-, an undescribed trace of the fading bird life of northeastern Brazil. Revista Brasileira de Ornithologia 22(2): 75-94.
Abstract: A new species of treehunter, Cichlocolaptes mazarbarnetti sp. nov., is described from a specimen that for many years had been confused with Philydor novaesi. The morphology of this specimen, collected in 1986 at Pedra Branca, Murici, Alagoas, at 550 m elevation (currently the Murici Ecological Station), suggests its allocation in the genus Cichlocolaptes. The new species differs from P. novaesi by its considerably larger size, heavier body-mass, darker and more uniform forehead and crown, absence of buffy periocular-feathers, and a pale orange-rufous tail that contrasts with the rump and the rest of the dorsal plumage. It also has a flat-crowned appearance and a larger, deeper-based, and generally stouter bill. Behavioral specialization on bromeliads and vocal repertoire also suggest that the new species belongs in the genus Cichlocolaptes. The song of this species is markedly different from that of P. novaesi, and it closely matches that of Cichlocolaptes leucophrus. The new species is endemic to the 'Pernambuco Center' of endemism, where it inhabits dense, humid forests in hilly terrain. It is known from only two localities in northeastern Brazil, one each in the states of Alagoas and Pernambuco. Taken together, these areas contain less than 3,000 ha of suitable habitat for the species, where we estimate the population during our studies to have numbered no more than 10 individuals. We propose that this species should be categorized as Critically Endangered at a national and global level, and we consider the situation of its conservation to be critical in that it will require urgent action to avoid its global extinction.
DesRochers, D. W., L. K. Butler, M. D. Silbernagle, and J. M Reed. 2009. Observations of molt in an endangered rallid, the Hawaiian Moorhen. Wilson Journal of Ornithology 121:148-153.
Abstract: We used field and museum data to describe timing of flight feather molt in the endangered Hawaiian Moorhen (Gallinula chloropus sandvicensis). We evaluated 80 adults captured a total of 107 times at two study sites on Oahu from April 2005 to August 2007. Eighty-five of the birds were not molting, 13 had abraded remiges, and eight of the nine molting adults examined were simultaneously replacing their primaries, secondaries, and upper and lower wing coverts. We also scored molt for 28 Hawaiian Moorhen specimens from three museum collections, but no birds were molting. Molt in Hawaiian Moorhens, which lasts about 30 days, was not synchronous across individuals with molting birds recorded from June to September in the field. We observed non-molting individuals throughout the year including birds we captured and museum specimens. Molting and nonmolting birds had similar body condition, as defined by mass/tarsometatarsal length. The flightless period during molt, which likely lasts about 25 days, may increase predation risk, a serious concern in Hawaii where introduced terrestrial predators pose a major threat to moorhen populations.
Desrochers, D. W., S. R. McWilliams, M. D. Silbernagle, and J. M Reed. 2009. Macronutrient profiles of wetland plants consumed by the Hawaiian Moorhen (Gallinula chloropus sandvicensis). Wetlands 29:845-853.
Abstract: Understanding the nutritional quality of wildlife foods is important for management and conservation efforts. We report the gross energy and macronutrient content of 10 plant species consumed by endangered Hawaiian Moorhens (Gallinula chloropus sandvicensis) along with gross energy and macronutrient content of three plant species not known to be consumed by moorhen. We also report the same information for Urochloa mutica that is consumed when it is 10 cm tall, but not when it is taller. We also compared macronutrient composition of plant species collected from sites with different soil moisture levels. Energy density, fat, ash, nitrogen, protein, carbohydrates, and fiber of these wetland plants were similar across soil moisture categories, but differed among plant species. We tested for rank consistency of nutrient values across species to determine if some were consistently high across measures, and we tested whether there were differences in energy and protein content between natives and nonnatives, and between species consumed versus not eaten. Rank values of macronutrients were inconsistent across species, and we found no differences in energy or protein across groups of species. Information on Hawaiian Moorhen nutritional requirements and the species’ ability to metabolize these different plants will help inform wetland managers.
DesRochers, D.W., S. R. McWillaims, and J. M. Reed. 2010. Evaluating if energy and protein limit abundance of Hawaiian Moorhen (Gallinula chloropus sandvicensis). Journal of Wildlife Management 74:788-795.
Abstract: Food abundance can affect a species’ distribution. In many studies of potential food limitation, researchers focus on carrying capacity estimates during the nonbreeding season for temperate species consuming a fixed food source. Estimates of energetic carrying capacity for year-round breeders feeding on a replenishing resource would be more difficult and require much data. To determine whether gathering detailed information on year-round carrying capacity would be an important investment, we conducted an assessment to determine whether there was evidence that energy or protein might limit numbers of the tropical, endangered Hawaiian moorhen (Gallinula chloropus sandvicensis). We compared observed numbers of moorhen at 15 Oahu, Hawaii, USA, wetlands with predicted numbers based on measured energy and protein in food plants and abundance of these food plants in each wetland and on estimates of energy expenditure of moorhen. We made comparisons assuming moorhen are limited by their ability to metabolize food plants, by competition for food, and by estimated costs associated with reproduction. We also compared ranked moorhen abundance and density with ranked energy and protein under different wetland management regimes. Energy values consistently overestimated expected numbers of Hawaiian moorhen at wetlands except for one wetland location (predicted, 3803 - 4856; observed, 6.2 - 10.8). In addition, we detected no significant relationship between moorhen abundance and measures of energy (all r2 > 0.02–0.73, all P < 0.1) or protein abundance (all r2 > 0.08–0.50, all P < 0.3). This lack of relationship held once we controlled for wetland area or when we considered whether wetlands were managed for waterbirds. Hawaiian moorhen on Oahu did not appear to be limited by energy, nor did they appear to select sites based on energy or protein, in contrast to many studies relating animal numbers to energy in nonbreeding situations. Consequently, we suggest that researchers and managers explore other potentially limiting factors for Hawaiian moorhen.
Frey, S.J.K., C.C. Rimmer, K.P. McFarland, and S. Menu. 2008. Identification and sex determination of Bicknell’s thrushes using morphometric data. Journal of Field Ornithology 79:408-420.
Abstract: The similar plumage of Bicknell's (Catharus bicknelli) and Gray-cheeked (C. minimus) Thrushes have hindered attempts to better understand the nonbreeding biology of these species. We used morphometric data, specifically primary formulae, from Bicknell's Thrushes of known sex and age throughout their breeding range in the United States and Canada to examine possible differences between sex and age classes. We compared these data with similar data from Gray-cheeked Thrushes in Alaska, United States and Newfoundland, Canada to examine mensural characters for distinguishing the two species. We performed a discriminant function analysis (DFA) for each age class to examine morphometric differences between male and female Bicknell's Thrushes. For second-year (SY) and after-second-year (ASY) birds, wing chord was the strongest differentiator, in conjunction with tarsus length. Wing chord and tail length were used to create a discriminant function to differentiate between the two Catharus species. The discriminant functions for both age classes did not permit unambiguous separation of male and female Bicknell's Thrushes nor did the DFA enable unequivocal species identity, but most individuals were correctly classified. Significant differences in the p8-p1 measurement of Bicknell's and Gray-cheeked Thrushes and of male and female Bicknell's Thrushes suggest that this character may be useful to augment published wing chord criteria for species identification and sex determination. Our results indicate that wing chord, in combination with tail length, is the most useful measurement for distinguishing Bicknell's from Gray-cheeked Thrushes and, when augmented with tarsus length, to differentiate between male and female Bicknell's Thrushes outside the breeding season.
Hennessey, A.B. 2011. Species rank of Phibalura (Flavirostris) boliviana based on plumage, soft part color, vocalizations, and seasonal movements. Wilson Journal of Ornithology 123:454-458.
Abstract: The Swallow-tailed Cotinga (Phibalura flavirostris) has traditionally been considered to consist of two subspecies, P. f. flavirostris of southeastern Brazil's foothill forest and, isolated by similar to 2,500 km, a population of P. f. boliviana in central-western Bolivia. The plumage of the two taxa is distinctly different; boliviana males have a longer tail, and body plumage is significantly less sexually dimorphic. The iris of boliviana is mustard yellow, distinct from the blood red iris of flavirostris. P. f. boliviana has dull to bright orange-yellow feet whereas flavirostris has pink feet. Only one vocalization type is recorded for P. f. flavirostris, whereas at least five calls and a song are known for P. f. boliviana, which vocalizes significantly more often. The Brazilian P. f. flavirostris has strong seasonal movements, whereas P. f. boliviana has no seasonal movements. Given the diagnosable differences between the two taxa, it is highly probable they are separate lineages. P. boliviana qualifies as critically endangered for its declining small population due to continual habitat loss.
Keyel, A. C., C. M. Bauer, C. R. Lattin, L. M. Romero, J. M. Reed. 2012. Testing the role of patch openness as a causal mechanism for apparent area sensitivity. Oecologia 169:407-418.
Abstract: Area sensitivity, species being disproportionately present on larger habitat patches, has been identified in many taxa. We propose that some apparently area-sensitive species are actually responding to how open a habitat patch is, rather than to patch size. We tested this hypothesis for Bobolinks (Dolichonyx oryzivorus) by comparing density and occupancy to a novel openness index, patch area, and edge effects. Bobolink density and occupancy showed significant relationships with openness, but logistic models based on an openness occupancy threshold had greater explanatory power. Thresholds remained approximately consistent from June through August, and shifted to be more open in September. Variance partitioning supported the openness index as unique and relevant. We found no relationships between measures of body condition (body mass, body size, circulating corticosterone levels) and either openness or area. Our findings have implications for studies of area sensitivity, especially with regards to inconsistencies reported within species: specifically, (1) whether or not a study finds a species to be area sensitive may depend on whether small, open sites were sampled, and (2) area regressions were sensitive to observed densities at the largest sites, suggesting that variation in these fields could lead to inconsistent area sensitivity responses. Responses to openness may be a consequence of habitat selection mediated by predator effects. Finally, openness measures may have applications for predicting effects of habitat management or development, such as adding wind turbines, in open habitat.
Keyel, A. C., D.T. Peck, and J. M. Reed. 2012. No evidence for individual assortment by temperament relative to patch area or patch openness in Bobolinks. Condor 114:212-218.
Abstract: Recent research has shown repeatable individual variability in temperament traits. We tested the hypotheses that individual Bobolinks (Dolichonyx oryzivorus) vary consistently in their response to predators, a temperament trait, and that this individual variation is associated with breeding-site selection. Specifically, we tested whether measures of behavioral response to human approaches are associated with either patch area or patch openness and thus to area sensitivity. We made two to seven sequential approaches to Bobolinks in 2009 and 2010, measuring starting distance, flight-initiation distance, and the distance from the observers to where the birds landed. We analyzed the data with repeatability estimates and linear mixed modeling. Flight-initiation distance was repeatable when starting distance was controlled for, but distance to landing was not after starting distance and flight-initiation distance were controlled for. We found no strong effect of area or openness on either flight initiation distance or distance to landing. We conclude that this measure of response to predators shows individual variation, but this variation does not explain patterns of settlement among habitat patches. Because flight-initiation distance is often used to identify distances at which human behavior disrupts wildlife, we estimate its mean (21.8 m) and the distance at which 75%, 95%, and 99% of the Bobolinks flushed (28, 40, and 59 m, respectively).
McFarland, K.P., Rimmer, C.C., Goetz, J.E., Aubry, Y., Wunderle, J.M. Jr., et al. 2013. A winter distribution model for Bicknell’s thrush (Catharus bicknelli), a conservation tool for a threatened migratory songbird. PLoS ONE 8(1): e53986.
Abstract: Conservation planning and implementation require identifying pertinent habitats and locations where protection and management may improve viability of targeted species. The winter range of Bicknell’s Thrush (Catharus bicknelli), a threatened Nearctic-Neotropical migratory songbird, is restricted to the Greater Antilles. We analyzed winter records from the mid-1970s to 2009 to quantitatively evaluate winter distribution and habitat selection. Additionally, we conducted targeted surveys in Jamaica (n = 433), Cuba (n = 363), Dominican Republic (n = 1,000), Haiti (n = 131) and Puerto Rico (n = 242) yielding 179 sites with thrush presence. We modeled Bicknell’s Thrush winter habitat selection and distribution in the Greater Antilles in Maxent version 3.3.1. using environmental predictors represented in 30 arc second study area rasters. These included nine land form, land cover and climatic variables that were thought a priori to have potentially high predictive power. We used the average training gain from ten model runs to select the best subset of predictors. Total winter precipitation, aspect and land cover, particularly broadleaf forests, emerged as important variables. A five-variable model that contained land cover, winter precipitation, aspect, slope, and elevation was the most parsimonious and not significantly different than the models with more variables. We used the best fitting model to depict potential winter habitat. Using the 10 percentile threshold (>0.25), we estimated winter habitat to cover 33,170 km2, nearly 10% of the study area. The Dominican Republic contained half of all potential habitat (51%), followed by Cuba (15.1%), Jamaica (13.5%), Haiti (10.6%), and Puerto Rico (9.9%). Nearly one-third of the range was found to be in protected areas. By providing the first detailed predictive map of Bicknell’s Thrush winter distribution, our study provides a useful tool to prioritize and direct conservation planning for this and other wet, broadleaf forest specialists in the Greater Antilles.
Miller-Rushing, A.J., R.B. Primack, & R. Stymeist. 2008. Interpreting variation in bird migration times as observed by volunteers. Auk 125:565-573.
Abstract: As a result of changes in climate over the past 100 years, many birds are arriving at points along their migration routes earlier in the spring now than they did in the past. Increasingly, researchers are relying on a variety of data sources, such as naturalist journals and bird-club records, to document migration times. However, it is not clear whether researchers can successfully use different sources of data to compare changes in migration times. We examined 25 years of changes in migration times for 30 species of birds at Mt. Auburn Cemetery in Cambridge, Massachusetts, as documented by bird-club members and published in a regional bird journal. We found that, overall, birds arrived earlier in warmer springs in eastern Massachusetts. We compared our findings with those of previous studies in Massachusetts, which included data from a standardized bird-banding station and observations from a naturalist’s journal and bird-club records. On a species-by-species basis, changes in migration times were not correlated among the studies. We believe that local changes in population sizes and sampling effort at some of the sites may have contributed to the lack of correlation. For the purpose of comparing changes in migration times across species and locations, standardized bird-banding data are preferable to data collected by volunteer naturalists. However, naturalist data sources are useful and reflect the widely observed trend toward earlier migrations in warm springs.
Nisbet, U.C.T., C.S. Mostello, R.R. Veit, J.W. Fox, and V. Afanasyev. 2011. Migrations and winter quarter of five common terns tracked using geolocators. Waterbirds 34:32-39.
Abstract: Ten geolocators (light-level data loggers) were attached to Common Terns (Sterna hirundo) at a breeding site in the northeastern USA in 2007 and 2008; six were retrieved (five with useful data) in 2008 and 2009. The birds wintered in four discrete areas on the north and east coasts of South America, from Guyana (6-7 degrees N) to northeastern Argentina (36-42 degrees S); three remained within restricted areas for most or all of the winter, whereas two ranged more widely. They left the breeding area at various dates between 1 August and 14 September; three migrated directly from the breeding area while two first moved southwest to stage near Cape Hatteras. All five birds flew directly to the vicinity of Puerto Rico, then moved along the north and east coasts of South America, staging at scattered locations for periods of 3-11 d, before reaching their winter quarters at various dates from 6 September to 26 October. Two birds left their winter quarters on 2 March and 4 April, staged in northern Brazil for 47 and 6 d, then traveled via the Bahamas to reach the breeding site on 1 May. During breeding and post-breeding periods, the birds spent a mean of 7 min each day and virtually no time at night resting on the water, but during the rest of the year they often rested on the water for up to 6 h by day and up to 11 h at night. Leg-mounted geolocators caused several adverse effects but did not reduce survival.
Primack, R.B., and A.J. Miller-Rushing. 2012. Uncovering, collecting, and analyzing records to investigate the ecological impacts of climate change: a template from Thoreau's Concord. BioScience 62:170-181.
Abstract: Historical records are an important resource for understanding the biological impacts of climate change. Such records include naturalists' journals, club and field station records, museum specimens, photographs, and scientific research. Finding records and overcoming their limitations are serious challenges to climate change research. In the present article, we describe efforts to locate data from Concord, Massachusetts, and provide a template that can be replicated in other locations. Analyses of diverse data sources, including observations made in the 1850s by Henry David Thoreau, indicate that climate change is affecting the phenology, presence, and abundance of species in Concord. Despite recent work on historical records, many sources of historical data are underutilized. Analyses of these data may provide insights into climate change impacts and techniques to manage them. Moreover, the results are useful for communicating local examples of changing climate conditions to the public.
Pruitt, M., and K. G. Smith. 2016. History and fall migration of Northern Saw-whet Owls (Aegolius acadicus) in Arkansas. Journal of the Arkansas Academy of Science 70:190-198.
Abstract: The secretive Northern Saw-whet Owl (Aegolius acadicus) is believed to be much more widespread during fall and winter than previously thought in the southern United States. To see if they occur more frequently in Arkansas, we initiated a banding study in fall of 2014 in northwestern Arkansas. Prior to that, only 12 historic records existed for Arkansas between 1959 and 2010. Over the course of two field seasons, we captured and banded 24 Northern Saw-whet Owls in rural Madison County. All birds were mist-netted along a trail, in woodland composed of pine and cedar with fairly dense undergrowth. Two were captured during our 2014 season when we started in late November and 22 were captured between late October and early December in 2015. We also had at least 10 birds vocalizing at our site. It would appear that the peak of migration in Arkansas is late October through early November, with capture rates dropping off by early December. All but one of the captured birds were females, the most common sex this far south. There was a fairly even distribution of hatch-year, second-year, and after-second-year birds and hatch-year birds and adults arrived at about the same time in late October and early November in 2015. Exactly where the owls are migrating from is unknown, although three foreign recoveries in Missouri and four recoveries in Arkansas suggest they are coming from the western Great Lakes region. Once considered a vagrant, based on our research, the Northern Saw-whet Owl appears to be an uncommon fall migrant, at least in the northwestern part of Arkansas. Comparing our data with that for central Missouri, about the same number of birds were captured at the same rates for about the same length of time, suggesting that Northern Saw-whet Owls are probably more common in the Ozarks than previously thought.
Renfrew, R.B., D. Kim, N. Perlut, J. Smith, J. Fox, and P. P. Marra. 2013. Phenological matching across hemispheres in a long-distance migratory bird. Diveristy and Distributions 19:1008-1019.
Abstract: In the Northern Hemisphere, bird migration from the tropic to the temperate zone in spring is thought to proceed at a rate determined in large part by local phenology. In contrast, little is understood about where birds go or the factors that determine why they move or where they stop during the post-breeding period. Study sites were in Oregon, Nebraska and Vermont, and location data we collected extend south to Argentina. We deployed light-level geolocators on individual Bobolinks from three populations across the breeding range and compare their southbound movement phenology to austral greening as indicated by the Normalized Difference Vegetation Index. Bobolinks from all breeding populations synchronously arrived and remained for up to several weeks in two sequential, small non-breeding areas that were separated by thousands of kilometres, before staging for pre-alternate moult. Similar to the migration patterns of birds to northern breeding areas, movements into the Southern Hemisphere corresponded to increasing primary productivity. Our findings suggest that the Bobolink’s southbound migration is broadly constrained by resource availability, and its non-breeding distribution has been shaped by the seasonal phenology of grasslands in both time and space. This is the first documentation of individual birds from across a continental breeding range exhibiting phenological matching during their post-breeding southward migration. Known conservation threats overlap temporally and spatially with large concentrations of Bobolinks, and should be closely examined. We emphasize the need to consider how individuals move and interact with their environment throughout their annual cycle and over hemispheric scales.
Rowher, S. 2013. Molt intensity and conservation of a molt migrant (Passerina ciris) in northwest Mexico. Condor 115:421-433.
Abstract: I describe primary replacement in molt-migrant Painted Buntings (Passerina ciris) captured during molt in northern coastal Sinaloa. Primary replacement is rapid, start dates vary substantially by year, and, especially in females, start and end dates for the molt overlap broadly in some years. The earliest adult females to initiate primary replacement start at the same time as adult males, but many females initiate molt very late, apparently because their mates desert late broods to migrate and molt early. These issues conspire to make traditional estimates of the duration of primary replacement invalid; thus, I calculate molt duration as D = L/G, where L is the summed length of independently grown primary and G is the primaries’ growth rate. Adult females replace their primaries in 30.3 (SE = 4.27) days, adult males in 34.3 (SE = 2.99) days. For 54 hatch-year birds that were molting when captured I calculated start dates for the eccentric molt to show, for the first time for any species, that young birds that initiate this partial replacement of primaries later in the season replace fewer feathers. The intensity of the primary molt in adult females, the sexual conflict that results in many females initiating molt much later than males, and recent habitat changes in coastal northwest Mexico, all conspire to suggest that the cause of the decline in the Midwestern breeding population of the Painted Bunting is likely related to recent increases in the mortality of adult females during their annual post-breeding molt.
Rohwer, S., K.A. Hobson, and V.G. Rowher. 2009. Migratory double breeding in Neotropical migrants. Proceedings of the National Academy of Sciences, 106:19050-19055.
Abstract: Neotropical migratory songbirds typically breed in temperate regions and then travel long distances to spend the majority of the annual cycle in tropical wintering areas. Using stable-isotope methodology, we provide quantitative evidence of dual breeding ranges for 5 species of Neotropical migrants. Each is well known to have a Neotropical winter range and a breeding range in the United States and Canada. However, after their first bout of breeding in the north, many individuals migrate hundreds to thousands of kilometers south in midsummer to breed a second time during the same summer in coastal west Mexico or Baja California Sur. They then migrate further south to their final wintering areas in the Neotropics. Our discovery of dual breeding ranges in Neotropical migrants reveals a hitherto unrealized flexibility in life-history strategies for these species and underscores that demographic models and conservation plans must consider dual breeding for these migrants.
Rohwer, S., K.A. Hobson, and S. Yang. 2011. Stable isotopes (delta D) reveal east-west differences in scheduling of molt and migration in northern rough-winged swallows (Stelgidopteryx serripennis). Auk 128:522-530.
Abstract: We used stable-isotope (delta D) measurements of primary feathers to demonstrate that Northern Rough-winged Swallows (Stelgidopteryx serripennis) that breed in western North America migrate to the monsoon region of northwest Mexico for their annual postbreeding molt. Both adults and juveniles replace all their primaries in late summer. As expected, in samples of adults and fledglings collected at a northern breeding locality in eastern Washington, primary delta D values of adults were of southern origin, whereas those of fledglings, whose feathers were grown in the nest, were consistent with their northern origin. Similarly, some young birds collected as they were replacing primaries in northwest Mexico had a southern signature in newly replaced primaries but a northern signature in their yet unreplaced juvenile primaries, which indicates that they were molt migrants from the north. Feather delta D values increased from P1 to P9 in breeding adults collected in upstate New York. In the eastern United States, both adults and juveniles replace their primaries as they migrate southward in the fall. These isotopic results are consistent with the observation that Northern Rough-winged Swallows are halfway through their primary molt when they reach the Gulf Coast, where they pause in coastal marshes to finish the primary molt before crossing the Gulf of Mexico. The striking difference in molt and migration schedules between eastern and western populations of Northern Rough-winged Swallows suggests further investigations of their species status be conducted in the region where these populations make contact.
Rohwer, S., V.G. Rohwer, A.T. Peterson, A.G. Navarro-Siguenza, and P. English. 2012. Assessing migratory double breeding through complementary specimen densities and breeding records. Condor 114:1-14.
Abstract: We re-evaluate the plausibility that five species of birds that breed in late summer in northwestern Mexico are migratory double breeders that first bred earlier in the same season to the north. We use data aggregated from scientific collections to generate abundance indices that adjust counts of specimens in collections by collecting effort, which we measure as the number of passerines collected in the same region and time period as the species of interest. Our abundance indices generally show displaced phenologies, such that presumed double breeders arrive and breed early in the north, then later in northwestern Mexico. We also compare breeding records for these regions, but these records could not be corrected for effort. Our phenologies suggest that the breeding populations of the Yellow-billed Cuckoo (Coccyzus americanus) from the western U.S. and northwestern Mexico may be derived from birds that bred earlier in eastern North America. Similarly, Orchard Orioles (Icterus spurius) breeding in late summer in northwestern Mexico and on the Mexican plateau may be derived from birds that attempted to breed earlier in North America. Our abundance indices and other new data suggest migratory double breeding is less likely in the Hooded Oriole (I. cucullatus) and probably not occurring in the Yellow-breasted Chat (Icteria virens) and Cassin’s Vireo (Vireo cassinii).
Rohwer, S., and C.S. Wood. 2013. Abundant early-summer breeding in Sinaloa does not suggest post-migratino breeding in three potential double breeders. Wilson Journal of Ornithology 125:243-250.
Abstract: Rohwer et al. (2009) present isotopic evidence of migratory double breeding by five species of birds that were breeding in July and August in northwestern Mexico. The presence of old brood patches in these species, combined with their late breeding in Mexico, suggested that these species had bred earlier in the north. Here we present data showing that Orchard Orioles and Yellow-breasted Chats breed as commonly in coastal Sinaloa in late May and early June as they do later in the summer; further, many females of these species examined in early June 2011 had downy ventral apteria, indicating that they were breeding for the first time in their annual cycle in Sinaloa. Thus, the old brood patches observed in these species in July and August, when they are still breeding in northwestern Mexico, may reflect earlier breeding attempts by those same individuals in Mexico. Yellow-billed Cuckoos seldom call and are uncommon in northwestern Mexico until late June and likely do not begin breeding until July. For Yellow-billed Cuckoos there had been no description of how the ventral apterium changes with breeding, so Rohwer et al. (2009) assumed that it followed a passerine pattern of refeathering during the post-breeding molt. To test this assumption we examined the ventral apterium in cuckoo specimens collected throughout the winter and found that it remains featherless throughout the year, including immediately after the complete mid winter molt. Thus, the bare ventral apteria of cuckoos arriving in northwestern Mexico in June and July do not constitute evidence of prior breeding in that year.
Silver, M., and C.R. Griffin. 2009. Nesting habitat characteristics of bank swallows and belted kingfishers on the Connecticut River. Northeastern Naturalist 16:519-534.
Abstract: Ceryle alcyon (Belted Kingfisher) and Riparia riparia (Bank Swallow) rely on vertical eroded banks for nesting. We inventoried Belted Kingfisher and Bank Swallow nesting banks along a 91.6-km section of the Connecticut River in Massachusetts, New Hampshire, and Vermont, including stretches where bank stabilization projects are completed, under construction, or planned. In the case of Bank Swallows, we also assessed the availability of potential nesting habitat in the study area. Forty-four Belted Kingfisher nesting sites and 12 Bank Swallow colonies were detected in the study area. Both species used banks with a low percentage of vegetative cover and a steep slope. Belted Kingfishers used high narrow banks. Bank Swallows used wide banks composed of well-drained, fine sandy loam soils. Potential Bank Swallow nesting sites were limited and in comparison to the sites actually used by Bank Swallows, they were narrower, more vegetated, and composed of more coarse soils. The impact of bank stabilization on Belted Kingfishers is probably minimal. However, bank stabilization eliminated three of twelve Bank Swallow colony sites that served as habitat for approximate to 20% of nesting pairs in the study area between 1999 and 2005.
Slay, C. M. and K. G. Smith. 2009. A comparison of nest success rates of four shrubland specialists in conservation managed fields to other managed and unmanaged shrublands. Pp. 705-712. In: T. Rich, C. Arizmendi, C. Thompson, and D. Demarest, eds. Tundra to Tropics: Birds, Habitats, and People. Proceedings of the Fourth International Partners in Flight Conference. Partners in Flight.
Abstract: Shrubland birds are disturbance dependent species and are experiencing population declines of 1–3%/year range wide. In our study, we determined nest success rates of four shrubland species, Blue-winged Warbler (Vermivora pinus), Prairie Warbler (Dendroica discolor), Indigo Bunting (Passerina cyanea), and Field Sparrow (Spizella pusilla), at Bent of the River Audubon Center, Southbury, Connecticut, USA. Field sites were conservation-managed fields that were actively managed for shrubland specialists. Data were collected on 123 nests (May–August, 2004–2006) and nest success rates (calculated using the Mayfield method) were 0.37 ± 0.003 for Blue-winged Warbler, 0.35 ± 0.013 for Prairie Warbler, 0.65 ± 0.009 for Indigo Bunting, and 0.50 ± 0.014 for Field Sparrow. Our study of these species is one of only three from the New England/ Mid-Atlantic Coast Region. We compiled data from studies from all regions reporting nest success of these species, conducted in a variety of managed and unmanaged shrublands. We compared our results to these studies and found nest success rates in conservation-managed fields to be similar to or higher than studies in different habitat management types in different regions. Based on our comparison of results from the limited number of studies on nest success rates of shrubland birds, the rotational mowing, selective tree removal, and invasive plant control regimes used to maintain conservation-managed shrublands are effective management practices to maintain high to moderate rates of nest success and may even be preferable to other management practices where shrubland species are targets for conservation.
Slay, C. M., K. S. Ellison, C. A. Ribic, K. G. Smith, and C. M. Schmitz. 2012. Nocturnal activity of nesting shrubland and grassland passerines. Pp. 105–116. In: C. A. Ribic, F. R. Thompson III, and P. J. Pietz, eds. Video Surveillance of Nesting Birds. Studies in Avian Biology no. 43.
Abstract: Nocturnal behaviors and sleep patterns of nesting passerines remain largely undocumented in the field and are important to understanding responses to environmental pressures such as predation. We used nocturnal video recordings to describe activity and quantify behaviors of females with nestlings of four shrub land bird species and three grassland bird species (n = 19 nests). Among the shrubland birds, Blue-winged Warbler (Vermivora pinus), Prairie Warbler (Setophaga discolor), and Indigo Bunting (Passerina cyanea) returned to the nest for the night at the same time, around sunset. Among the grassland birds, Eastern Meadowlark (Sturnella magna) returned the earliest before sunset and Grasshopper Sparrow (Ammodramus savannarum) returned the latest after sunset. All species exhibited "back sleep" with the bill tucked under scapular feathers, and individuals awoke frequently for vigils or "peeks" at their surroundings. Sleep of all species was disrupted by nestling activity. Average duration of sleep bouts varied from 6 min (Grasshopper Sparrow) to 28 min (Blue-winged Warbler; Field Sparrow (Spizella pusilla). Mean overnight duration on the nest varied from 6.4 hr (Field Sparrow) to 8.8 hr (Indigo Bunting). On average, adults woke in the morning (the last waking before departing the nest) 20-30 min before sunrise. The first absence from the nest in the morning was short for all species, and nestlings were fed within 12 min of a parent's departure. Our study highlights the need for further video research on sleep patterns of nesting birds in the field to better understand basic natural history, energetic cost-benefits of sleep, and behavioral adaptations to environmental pressures.
Sly, N.D., A.K. Townsend, C.C. Rimmer, J.M. Townsend, C.C. Latta, and I.J. Lovette. 2010. Phylogeography and conservation of the endemic Hispaniolan Palm-Tanagers (Aves: Phaenicophilus). Conservation Genetics 11:2121-2129.
Abstract: The Gray-crowned Palm-Tanager (Phaenicophilus poliocephalus), sometimes considered conspecific with its more widespread congener P. palmarum, is restricted to Haiti's Tiburon Peninsula, a biodiversity hotspot threatened by extensive habitat loss. We used a multilocus phylogeographic approach to identify evolutionarily distinct populations of Phaenicophilus. Mitochondrial haplotypes formed two reciprocally monophyletic groups separated by 5% uncorrected divergence. Genealogical patterns of differentiation at nuclear intron alleles were congruent with those of mtDNA, and the two species also differed in body size and shape. An ancient sea channel between the Tiburon Peninsula and mainland Haiti was likely a dispersal barrier that led to allopatric divergence, a hypothesis supported by our estimates of divergence times. Our results support the recognition of two Palm-Tanager species, confirming P. poliocephalus as Haiti's only endemic bird species and underscoring the need to protect the Tiburon Peninsula's single primary forest reserve.
Sly, N.D., A.K. Townsend, C.C. Rimmer, J.M. Townsend, C.C. Latta, and I.J. Lovette. 2011. Ancient islands and modern invasions: disparate phylogeographic histories among Hispaniola’s endemic birds. Molecular Ecology 20:5012-5024.
Abstract: With its large size, complex topography and high number of avian endemics, Hispaniola appears to be a likely candidate for the in situ speciation of its avifauna, despite the worldwide rarity of avian speciation within single islands. We used multilocus comparative phylogeography techniques to examine the pattern and history of divergence in 11 endemic birds representing potential within-island speciation events. Haplotype and allele networks from mitochondrial ND2 and nuclear intron loci reveal a consistent pattern: phylogeographic divergence within or between closely related species is correlated with the likely distribution of ancient sea barriers that once divided Hispaniola into several smaller paleo-islands. Coalescent and mitochondrial clock dating of divergences indicate species-specific response to different geological events over the wide span of the islands history. We found no evidence that ecological or topographical complexity generated diversity, either by creating open niches or by restricting long-term gene flow. Thus, no true within-island speciation appears to have occurred among the species sampled on Hispaniola. Divergence events predating the merging of Hispaniolas paleo-island blocks cannot be considered in situ divergence, and postmerging divergence in response to episodic island segmentation by marine flooding probably represents in situ vicariance or interarchipelago speciation by dispersal. Our work highlights the necessity of considering island geologic history while investigating the speciationarea relationship in birds and other taxa.
Studds, C.E., K.P. McFarland, Y. Aubry, C.C. Rimmer, K.A. Hobson, P.P. Marra, and L.I. Wassenaar. 2012. Stable-hydrogen isotope measures of natal dispersal reflect observed population declines in a threatened songbird. Diversity and Distributions 18:919-930.
Abstract: Measuring dispersal is crucial for estimating demographic rates that inform conservation plans for rare and threatened species. We evaluated natal dispersal patterns in Bicknell's thrush (Catharus bicknelli) across most of the breeding range using a 10-year data set of stable-hydrogen isotope ratios in feathers (d2HF) grown on the natal area and sampled 1 year later at the first breeding site. North-eastern United States and south-eastern Canada. We used d2HF values of adult thrushes sampled at 25 breeding sites as prior information for assigning first-time breeders to their natal site. We calculated the minimum distance birds moved from their natal to first breeding site and fit these data to three statistical distributions for characterizing the importance of long-distance dispersal: the exponential, Weibull and half-Cauchy. Finally, we assessed differences in the probability of dispersal across the breeding range and through time to understand spatio-temporal variation in demographic connectivity. The d2HF values of first-time breeders were lower compared with those of adults, a difference that was greater at the southern compared with northern breeding range extreme. Assignment tests accounting for age differences in d2HF suggested that most birds dispersed < 200 km from their natal area and within the centre of the breeding range, whereas comparatively few individuals dispersed up to 700 km. A Weibull distribution provided the best fit to these data. Two of three corrections for age differences in d2HF indicated that natal dispersal probability declined by 3038% from 1996 to 2005. Our findings suggest that estimating natal dispersal with d2HF measurements may contribute to understanding the resilience of geographically isolated Bicknell's thrush populations. Declining natal dispersal may be symptomatic of observed population declines and could compound this trend by limiting demographic exchange between habitat patches predicted to be increasingly isolated by natural and anthropogenic habitat changes.
Tavernia, B. G., and J. M. Reed. 2009. Spatial extent and habitat context influence the nature and strength of relationships between urbanization measures. Landscape and Urban Planning 92:47-52.
Abstract: A wide variety of metrics is used to quantify features of urbanization in ecological studies. Selecting statistically independent measures of urbanization depends upon the nature (multivariate collinearity) and strength (correlation coefficient) of correlations between urban metrics.We evaluated the influence of landscape extent and habitat context, factors that commonly differ between studies, on correlations between urban metrics. We examined the nature and strength of relationships between urban metrics at 1105 sites within Massachusetts, USA, including: population, agriculture cover, forest cover, wetland cover, dense residential cover, impervious surface cover, road length and greenspace cover. At each site, values were measured at five extents: 100m, 250 m, 500m, 1 km, and 2 km radii buffers. We also investigated the influence of habitat context on correlations by measuring values with a 1km radius buffer for 100 sites within each of three habitat contexts (salt marsh, forest, and freshwater marsh). Principal component analysis showed that spatial scale did not affect the nature of relationships, but habitat context did. The average strength of bivariate correlations significantly increased at larger extents, and was significantly lower in salt marsh habitat context. Our results indicate that no single set of urbanization metrics is universally applicable and underline the importance of using a suite of statistical techniques to characterize independent aspects of urban environments.
Tavernia, B. G., and J. M. Reed. 2010. Spatial, temporal, and life history assumptions influence consistency of landscape effects on species distributions. Landscape Ecology 25:1085-1097.
Abstract: Models describing relationships between landscape features and species distribution patterns often display inter-study inconsistencies. Identifying factors contributing to these inconsistencies is a vital step in clarifying the ecological importance of landscape features and synthesizing an effective knowledge base for use in conservation contexts. We examined the influence of several spatial, temporal, and life history assumptions on the outcomes of distribution versus landscape models (DLMs) relating wetland bird communities at 29 Massachusetts (USA) sites to independent urbanization, wetland, forest, and agricultural landscape gradients. We considered a bird specialization index as well as obligate and facultative species richness as response variables. Landscape gradients were quantified at 10 landscape extents (0–1000 m in 100 m increments) and three time periods (1971, 1985, 2005). Univariate models indicated that our specialization index showed: (1) the strongest response to landscape gradients at small extents (200 m); (2) a negative, threshold response to urbanization was superior to a linear fit; and (3) no evidence of time-lagged effects of landscape change. Interestingly, the form of our model (i.e. linear versus threshold) influenced the extent at which strongest effects were detected. Multivariate models relating the specialization index as well as obligate and facultative species richness to landscape gradients showed evidence of annual variability (i.e. composition, parameter estimates, and variability explained) that did not depend upon an organism’s degree of specialization. Our results provide evidence that violations of common assumptions (e.g. selection of appropriate extent, lack of time-lagged effects, etc.) can impact the outcome of DLMs, which could lead to inter-study inconsistencies.
Tavernia, B. G., and J. M. Reed. 2012. The impact of purple loosestrife (Lythrum salicaria) on wetland bird distributions. American Midland Naturalist 168:352-363.
Abstract: The exotic invasive wetland plant purple loosestrife (Lythrum salicaria) is often considered to have negative impacts on native plant and animal species, but this is debated. Clarifying its influence would provide insight into appropriate management actions following invasion. We investigated the influence of L. salicaria cover and density on abundances of wetland bird species that are associated with a variety of vegetation structures. We found evidence of relationships between L. salicaria measures and abundance for most species we examined, but these relationships did not always agree with our predictions based on species’ habitat associations. Some bird species positively responded whereas others negatively responded to increasing L. salicaria cover or density. Response curves varied in complexity and included linear and quadratic relationships as well as interactions. Our results suggested that L. salicaria did not categorically decrease habitat quality for all wetland bird species, and it may have had a positive influence on quality for some species. This ambiguity is not unique to L. salicaria invasion but applies to many changing habitat features. Therefore, there is likely no single appropriate strategy for managing L. salicaria when the goal is to maintain a diverse avian community in which species have divergent habitat preferences.
Townsend, J.M., C.C. Rimmer, A.K. Townsend, and K.P. McFarland. 2011. Sex and age ratios of Bicknell's thrush wintering in Hispaniola. Wilson Journal of Ornithology 123:367-372.
Abstract: We investigated sex and age ratios of wintering Bicknell's Thrush (Catharus bicknelli) across a geographic gradient of sites on Hispaniola. The island-wide proportion male was 0.64 (n = 127), which is comparable to the known male bias in breeding areas. The proportion male varied geographically on Hispaniola, suggesting some level of habitat segregation. Male-biased ratios occurred at two sites whereas sex ratios at five sites did not differ from parity. The island-wide proportion adult was 0.72 and age ratios were significantly adult-biased at two sites. We assessed vegetative structure at all sites and the proportion of male thrushes increased significantly with density of understory vegetation. Age ratios were not associated with vegetation characteristics. Neither sex nor age ratios varied significantly with elevation. Our data suggest the possibility of sexual habitat segregation with males preferentially occupying cloud forest sites characterized by a thick understory of vines and saplings occurring at densities >10,000 stems/ha.
Watson, M.J., J.A. Spendelow, and J.J. Hatch. 2012. Post-fledging brood and care division in the roseate tern (Sterna dougallii). Journal of Ethology 30:29-34.
Abstract: Extended post-fledging parental care is an important aspect of parental care in birds, although little studied due to logistic difficulties. Commonly, the brood is split physically (brood division) and/or preferential care is given to a subset of the brood by one parent or the other (care division). Among gulls and tern (Laridae), males and females generally share parental activities during the pre-fledging period, but the allocation of parental care after fledging is little documented. This study examined the behaviour of male and female roseate terns (Sterna dougallii) during the late chick-rearing and early post-fledging periods, and in particular the amount of feeds and the time spent in attendance given to individual chicks/fledglings. Pre-fledging parental care was biparental in all cases. Post-fledging parental care was dependent on the number of fledglings in the brood. Males and females continued biparental care in clutches with one surviving fledgling, while in two-fledgling clutches, males fed the A-fledgling while females fed the B-fledgling. Overall, there was no difference in attendance, only in feeds. This division of care may be influenced by the male only being certain of the paternity of the A-chick but not by chick sex.