Species Of Wood Warblers Research Articles

A late burst of colour evolution in a radiation of songbirds (Passeriformes: Parulidae) suggests secondary contact drives signal divergence.

Evolutionary radiations provide important insights into species diversification, which is especially true of adaptive radiations. New World wood warblers (Parulidae) are a family of small, insectivorous, forest-dwelling passerine birds, often considered an exemplar of adaptive radiation due to their rapid diversification followed by a slowdown. However, they deviate from the expectations of an adaptive radiation scenario due to the lack of conspicuous morphological and ecological differentiation. We fitted several macroevolutionary models to trait data in 105 species of wood warblers. We tested whether morphological traits underwent an early burst of evolution (suggesting adaptation to new ecological niches in adaptive radiations) and whether song and colour underwent a diversity-dependent acceleration of trait evolutionary rate (consistent with reproductive interference driving signal evolution). Morphology and song evolved gradually under stabilizing selection, suggesting niche conservatism, with morphology possibly acting as a constraint on song evolution. In contrast, many feather colour traits underwent a diversity-dependent burst of evolution occurring late in the clade's history. We suggest that a two-step process has led to the remarkable diversification of wood warblers. First, their early diversification probably proceeded by allopatric speciation. Second, feather colour divergence likely occurred during secondary contact after range expansion. This diversification of signalling traits might have facilitated species coexistence, in combination with behavioural niche partitioning. Wood warblers seem to present characteristics of both adaptive and non-adaptive radiations.

Gut microbiome composition better reflects host phylogeny than diet diversity in breeding wood-warblers.

Understanding the factors that shape microbiomes can provide insight into the importance of host-symbiont interactions and on co-evolutionary dynamics. Unlike for mammals, previous studies have found little or no support for an influence of host evolutionary history on avian gut microbiome diversity and instead have suggested a greater influence of the environment or diet due to fast gut turnover. Because effects of different factors may be conflated by captivity and sampling design, examining natural variation using large sample sizes is important. Our goal was to overcome these limitations by sampling wild birds to compare environmental, dietary and evolutionary influences on gut microbiome structure. We performed faecal metabarcoding to characterize both the gut microbiome and diet of 15 wood-warbler species across a 4-year period and from two geographical localities. We find host taxonomy generally explained ~10% of the variation between individuals, which is ~6-fold more variation of any other factor considered, including diet diversity. Further, gut microbiome similarity was more congruent with the host phylogeny than with host diet similarity and we found little association between diet diversity and microbiome diversity. Together, our results suggest evolutionary history is the strongest predictor of gut microbiome differentiation among wood-warblers. Although the phylogenetic signal of the warbler gut microbiome is not very strong, our data suggest that a stronger influence of diet (as measured by diet diversity) does not account for this pattern. The mechanism underlying this phylogenetic signal is not clear, but we argue host traits may filter colonization and maintenance of microbes.

The Complete Genome Sequence of Protonotaria citrea, the Prothonotary Warbler.

The Prothonotary Warbler (Protonotaria citrea) is a nearctic-neotropical migratory songbird that breeds in forested swamps and riparian areas in the eastern-central United States and southern Ontario. It is the sole eastern North American wood-warbler that nests in cavities, the only species in the genus Protonotaria, and is one of the few hole-nesting hosts of the Brown-headed Cowbird (Molothrus ater), an obligate brood parasite. We present the whole genome sequence of this wood-warbler species. Illumina sequencing was performed on a genetic sample from a single female individual. The reads were assembled using a de novo method followed by a finishing step. The raw and assembled data is publicly available via Genbank: Sequence Read Archive (SRR19579445) and Assembly (JAOYNP000000000).

Comparative cytogenetics in three species of Wood-Warblers (Aves: Passeriformes: Parulidae) reveal divergent banding patterns and chromatic heterogeneity for the W chromosome

Chromosomal rearrangements are an important process in the evolution of species. It is assumed that these rearrangements occur near repetitive sequences and heterochromatic regions. Avian karyotypes have diverse chromosomal band patterns and have been used as the parameters for phylogenetic studies. Although the group has a high diversity of species, no more than 12% has been analyzed cytogenetically, and the Parulidae family are extremely underrepresented in these studies. The aim of this study was to detect independent or simultaneous chromosomal rearrangements, and also to analyze chromosomal banding convergences and divergences of three Wood-Warblers species (Myiothlypis leucoblephara, Basileuterus culicivorus, and Setophaga pitiayumi). Our CBG-band results reveal an unusual W sex chromosome in the three studied species, containing a telomeric euchromatic region. The GTG and RBG bands identify specific regions in the macrochromosomes involved in the rearrangements. Cytogenetic data confirm the identification of speciation processes at the karyotypic of this group.

The evolution of wood warbler flight calls: Species with similar migrations produce acoustically similar calls.

Diverse animal species engage in long-distance migrations. Many migrants travel in groups, and communication within these groups may be important to survival and successful migration. We examined migration and communication in 36 species of wood warblers (Parulidae), songbirds that breed in North America and migrate in mixed-species flocks to their wintering grounds. During migration, wood warblers produce short vocalizations called "flight calls." The function of flight calls and the patterns of acoustic similarity between species are poorly understood. We investigated whether acoustic similarity of flight calls of different species of warbler reflects the similarity in their migratory journeys or their phylogenetic relatedness. We found that phylogeny, similarity in breeding latitude, and overlap in the timing of migration predict acoustic flight call similarity across warbler species. Further, we found that phylogeny, similarity in migration distance, and overlap in wintering range predict acoustic flight call similarity in a subset of 12 species with highly similar calls, although this analysis has a small sample size. We conclude that migratory similarity may be an important force driving the evolution of acoustically similar calls in wood warblers, in addition to phylogenetic relatedness. Acoustic convergence in these species may facilitate communication between individuals with similar migrations.

Natural and sexual selection shape the evolution of colour and conspicuousness in North American wood-warblers (Parulidae)

AbstractNatural and sexual selection drive colour evolution in animals. However, these different selective forces are often studied independently or without considering environmental variation. We evaluated the roles of natural and sexual selection together on colour evolution in 15 sympatric wood-warbler species, while considering the influence of variation in the light environment and visual background. We tested the influence of each selective pressure on male and female coloration and contrast against the background using avian visual models in phylogenetically controlled analyses. We found natural and sexual selection simultaneously driving cryptic and conspicuous plumage in males by acting on different body regions. For example, we found that ground-nesting species had males with conspicuous under-body plumage and cryptic upper-body plumage, showing how natural and sexual selection can drive colour evolution concordantly. We also found interesting relationships with female plumage, such as nest predation positively covarying with female contrast against the background, suggesting a cost to female conspicuousness. Our findings here showcase the complexity of selection on coloration and illustrate the importance of: (1) accounting for environmental variation when assessing how natural and sexual selection drive colour evolution; and (2) testing how multiple selection pressures are shaping colour diversity among species.

Decoding the ‘zeep’ complex: quantitative analysis of interspecific variation in the nocturnal flight calls of nine wood warbler species (Parulidae spp.)

ABSTRACTThe “zeep” complex consists of nine birds that produce nocturnal flight calls with similar acoustic features. Our inability to distinguish these calls inhibits the acoustic monitoring of these species. We test the hypothesis that flight calls of nine warblers in the “zeep” complex show sufficient acoustic differences to allow differentiation. We investigate divergence in these vocalizations by recording birds held for banding and collecting additional recordings from sound libraries. We used three approaches to compare calls between species: analysis of variance in acoustic properties, discriminant analysis of acoustic properties, and spectrographic cross-correlation. The first approach revealed five species that were different in one or more acoustic properties. The second approach revealed a level of assignment to the correct species (73%) that exceeded levels expected by chance (36%). The third approach revealed calls of seven species to be significantly more similar to conspecific calls than heterospecific calls. Our results suggest the calls of many members of the “zeep” complex exhibit species-specific differences in structure, which may allow differentiation of at least five “zeep” species based on call alone. We advocate for the combined use of these three approaches for the comparison of “zeep” calls in future flight call studies.

Habitat suitability and the constraints of migration in New World warblers

Identifying the factors that influence geographic range limits can illustrate the various ecological, physiological, and evolutionary constraints imposed on a species. The range limits of migratory birds are particularly challenging to study as they occur in disjunct regions at different times of the year, which can impose different constraints. Travel between breeding and wintering regions poses a significant energetic and navigational challenge to birds, although it is not clear how these movements influence breeding dispersal and range expansion. Here I ask whether the possible costs of migration limit the breeding ranges of wood warblers, a group of birds with an extensive history of ecological and evolutionary studies. I used occurrence records for multiple wood warbler species, breeding primarily in the boreal forest of North America, to generate environmental niche models. I tested for over‐prediction of habitat suitability into the western boreal forest, where most these species do not have occurrence records but where there is presumably suitable habitat. I found that some of these vagile taxa, primarily found east of the Rocky Mountains, also have predicted habitat suitability that extends into the north and west, where they have little to no occurrence records. I discuss several possible explanations for this discordance. In particular, the patterns are consistent with the costs of a long‐distance migration limiting the benefits of range expansion, as migration may become too onerous as the distance between breeding and wintering areas increases. These results speak to the process of niche filling more generally and call attention to an under‐appreciated explanation for why migratory species may not fully occupy their fundamental niche.

Tree Species Preferences of Foraging Songbirds During Spring Migration in Floodplain Forests of the Upper Mississippi River

Floodplain forest of the Upper Mississippi River is important for songbirds during spring migration. However, the altered hydrology of this system and spread of reed canary grass (Phalaris arundinacea) and emerald ash borer (Agrilus planipennis) threaten tree diversity and long-term sustainability of this forest. We estimated tree preferences of songbirds during spring migration 2010–2013 to help guide management decisions that promote tree diversity and forest sustainability and to evaluate yearly variation in tree selection. We used the point center-quarter method to assess relative availability of tree species and tallied bird foraging observations on tree species as well as recording the phenophase of used trees on five 40 ha plots of contiguous floodplain forest between La Crosse, Wisconsin and New Albin, Iowa, from 15 April through 1 June. We quantified bird preferences by comparing proportional use of tree species by each bird species to estimates of tree species availability for all 4 y and for each year separately. Species that breed locally preferred silver maple (Acer saccharinum), which is dominant in this forest. The common transient migrant species and the suite of 17 transient wood warbler species preferred hackberry (Celtis occidentalis) and oaks (Quercus spp.), which are limited to higher elevations on the floodplain. We observed earlier leaf development the warm springs of 2010 and 2012 and later leaf development the cold springs of 2011 and 2013. Yellow-rumped Warbler (Setophaga coronata), American Redstart (S. ruticilla), Warbling Vireo (Vireo gilvus) and Baltimore Oriole (Icterus galbula), and the suite of transient migrant wood warblers spread their foraging efforts among tree species in colder springs and were more selective in warmer springs. All three of the important tree species are not regenerating well on the UMR and widespread die-off of silver maple is possible in 50 y without large scale management.

Age-Ratios and Condition of En Route Migrant Blackpoll Warblers in the British Virgin Islands

ABSTRACT The en route migration ecology of Blackpoll Warblers (Setophaga striata) is poorly understood, yet intriguing. Blackpoll Warblers undertake the longest open water migration of any wood warbler species, traveling from northeastern North America to South America, with the first potential landfall being the West Indies. This migration requires substantial energy reserves and subjects Blackpoll Warblers to unpredictable weather events, which may influence survival. Few studies have examined age ratios or condition of Blackpoll Warblers while the warblers are en route through the Caribbean region. I captured and banded Blackpoll Warblers in the British Virgin Islands over 10 consecutive autumn migrations. Ratios of hatch-year to adult Blackpoll Warblers were variable but averaged lower than the ratios reported at continental departure locations. Average mass of Blackpoll Warblers was less than that reported at continental departure locations, with 26% of adults and 40% of hatch-year birds below the es...

Two song categories in the Canada Warbler (Cardellina canadensis)

ABSTRACT. North American wood-warbler species (Parulidae) studied to date have song systems of one or two categories. Those with two categories use them in different temporal and behavioral contexts, which suggests similar functions across species. We conducted the first detailed analysis of the vocal behavior of a species in the genus Cardellina, the Canada Warbler (C. canadensis). We found that males had two performance-encoded song categories, Mode I and Mode II, and used them in contexts similar to those in which parulids of the genera Vermivora, Mniotilta, and Setophaga use their song categories. Males sang Mode I more often during the day, when unpaired, during early nesting, and when alone or near a female. Males sang Mode II at dawn, after pairing, during the postfledging period, and when near another male. In Mode I, males sang more stereotyped songs more slowly and regularly. In Mode II, males sang more variable songs rapidly, with a more variable rhythm, and chipped frequently between songs. Al...

Ancestry and evolution of seasonal migration in the Parulidae

Seasonal migration in birds is known to be highly labile and subject to rapid change in response to selection, such that researchers have hypothesized that phylogenetic relationships should neither predict nor constrain the migratory behaviour of a species. Many theories on the evolution of bird migration assume a framework that extant migratory species have evolved repeatedly and relatively recently from sedentary tropical or subtropical ancestors. We performed ancestral state reconstructions of migratory behaviour using a comprehensive, well-supported phylogeny of the Parulidae (the 'wood-warblers'), a large family of Neotropical and Nearctic migratory and sedentary songbirds, and examined the rates of gain and loss of migration throughout the Parulidae. Counter to traditional hypotheses, our results suggest that the ancestral wood-warbler was migratory and that losses of migration have been at least as prevalent as gains throughout the history of Parulidae. Therefore, extant sedentary tropical radiations in the Parulidae represent losses of latitudinal migration and colonization of the tropics from temperate regions. We also tested for phylogenetic signal in migratory behaviour, and our results indicate that although migratory behaviour is variable within some wood-warbler species and clades, phylogeny significantly predicts the migratory distance of species in the Parulidae.

A comprehensive multilocus phylogeny for the wood-warblers and a revised classification of the Parulidae (Aves)

The birds in the family Parulidae—commonly termed the New World warblers or wood-warblers—are a classic model radiation for studies of ecological and behavioral differentiation. Although the monophyly of a ‘core’ wood-warbler clade is well established, no phylogenetic hypothesis for this group has included a full sampling of wood-warbler species diversity. We used parsimony, maximum likelihood, and Bayesian methods to reconstruct relationships among all genera and nearly all wood-warbler species, based on a matrix of mitochondrial DNA (5840 nucleotides) and nuclear DNA (6 loci, 4602 nucleotides) characters. The resulting phylogenetic hypotheses provide a highly congruent picture of wood-warbler relationships, and indicate that the traditional generic classification of these birds recognizes many non-monophyletic groups. We recommend a revised taxonomy in which each of 14 genera (Seiurus, Helmitheros, Mniotilta, Limnothlypis, Protonotaria, Parkesia, Vermivora, Oreothlypis, Geothlypis, Setophaga, Myioborus, Cardellina, Basileuterus, Myiothlypis) corresponds to a well-supported clade; these nomenclatural changes also involve subsuming a number of well-known, traditional wood-warbler genera (Catharopeza, Dendroica, Ergaticus, Euthlypis, Leucopeza, Oporornis, Parula, Phaeothlypis, Wilsonia). We provide a summary phylogenetic hypothesis that will be broadly applicable to investigations of the historical biogeography, processes of diversification, and evolution of trait variation in this well studied avian group.

A phylogenetic approach to disentangling the role of competition and habitat filtering in community assembly of Neotropical forest birds

1. Methods that assess patterns of phylogenetic relatedness, as well as character distribution and evolution, allow one to infer the ecological processes involved in community assembly. Assuming niche conservatism, assemblages should shift from phylogenetic clustering to evenness with decreasing geographic scale because the relative importance of mechanisms that shape assemblages is hypothesized to be scale-dependent. Whereas habitat filtering is more likely to act at regional scales because of increased habitat heterogeneity that allows sorting of ecologically similar species in contrasting environments, competition is more likely to act at local scales because low habitat heterogeneity provides few opportunities for niche partitioning. 2. We used species lists to assess assemblage composition, data on ecologically-relevant traits, and a molecular phylogeny, to examine the phylogenetic structure of antbird (Thamnophilidae) assemblages at three different geographical scales: regional (ecoregions), intermediate (100-ha plots) and local (mixed-flocks). In addition, we used patterns of phylogenetic beta diversity and beta diversity to separate the factors that structure antbird assemblages at regional scales. 3. Contrary to previous findings, we found a shift from phylogenetic evenness to clustering with decreasing geographical scale. We argue that this does not reject the hypothesis that habitat filtering is the predominant force in regional community assembly, because analyses of trait evolution and structure indicated a lack of niche conservatism in antbirds. 4. In some cases, phylogenetic evenness at regional scales can be an effect of historical biogeographic processes instead of niche-based processes. However, regional patterns of beta diversity and phylogenetic beta diversity suggested that phylogenetic structure in our study cannot be explained by the history of speciation and dispersal of antbirds, further supporting the habitat-filtering hypothesis. 5. Our analyses suggested that competitive interactions might not play an important role locally, which would provide a plausible explanation for the high alpha diversity of antbirds in Amazonia. 6. Finally, we emphasize the importance of including trait information in studies of phylogenetic community structure to adequately assess the mechanisms that determine species co-existence.

Assessing Landbird Monitoring Programs and Demographic Causes of Population Trends

Abstract: Population trend data from the North American Breeding Bird Survey (BBS) have been used to identify conservation priorities and justify major conservation initiatives. Yet the BBS has been criticized for potential habitat bias and reliance on abundance indices to estimate trends. We compared 1992–2003 BBS trend estimates to trend estimates derived from bird‐banding data collected as part of the Monitoring Avian Productivity and Survivorship (MAPS) program for 36 wood warbler species. Similarity in trends between the 2 monitoring programs at the survey‐wide and program‐wide scales suggested that each program can provide accurate trend information. The MAPS program, however, was designed primarily to complement (rather than duplicate) count‐based efforts, such as the BBS, by providing estimates or indices of demographic rates. Demographic data from MAPS can be used to lend insight into proximate (demographic) causes of population trends and inform management. We illustrate this with analyses of 1992–2003 MAPS data for yellow warbler (Dendroica petechia). We used reverse‐time capture‐recapture models to evaluate importance of new recruits (including immigrating adults and young from the previous year) relative to surviving adults in explaining variation in trend among BBS physiographic strata. We included the number of young per adult captured (an index of productivity) as a covariate in models to assess effects of productivity on trends. Survival was the key demographic driver of recent population trends. Comparison of MAPS productivity indices and adult apparent survival rate estimates to BBS trend estimates largely confirmed this inference. We suggest that increased MAPS coverage, better coordination between MAPS and the BBS, and continued development of analytical methods that link the 2 programs will enhance the value of these monitoring efforts to land managers and conservation planners working at a variety of spatial scales.

Nocturnal Migrants Foraging at Night by Artificial Light

Artificial lights can have detrimental effects on nocturnal migrant birds and other wildlife, yet some species of typically diurnal insectivorous birds are capable of foraging at night under artificial illumination. Here, we report observations of at least 15 wood-warbler species (Parulidae), one tyrant-flycatcher (Tyrannidae), and one mimid (Mimidae) foraging at night in areas illuminated by powerful artificial lights. To our knowledge, our observations represent the first report of a mixed-species flock of birds foraging on insects attracted to artificial lights or within foliage illuminated by artificial lights at night.

Moving From Fringe to Mainstream

Just below the 60th parallel and well above the 40th parallel there is a place where bird watchers, First Nation peoples, and "Big Oil" mingle. What would otherwise be considered unlikely is relative in this land where sand dunes exist in tandem with wetlands and a boreal forest, and cold snaps bring temperatures to −40°F. The Canadian landscape just south of the Northwest Territory is a nature artist's study in the unlikely. It is here, in the northern city of Fort McMurray, that oil companies—small and large, state-owned and independent—are strategically flocking into a fast-changing energy landscape. In the 1990s, when oil was trading at U.S. $12/bbl, it was unlikely that Canada would witness such a rapid step-up in heavy-oil and oil-sands development. Now conventional oil is on its way to being displaced by synthetic crudes built by 19 separate heavy-oil streams currently being marketed out of western Canada (Fig. 1). Oil sands now account for 39% of Canada's total oil production at approximately 1 million BOPD. By 2020, production could grow to 4 million BOPD. No Longer a Footnote Alberta's oil-sands deposits contain one-third of all known oil reserves in the world, according to the Oil Sands Discovery Center, and are one of the few remaining developments still open to private investment (Fig. 2). The most northerly dune complex in the world exists in Canada; the dunes can reach 35 m in height. Beneath these dunes lies a small percentage of Canada's heavy oil. The largest percentage of heavy-oil reserves lies beneath muskeg, either close enough to the surface to be mined economically by removing the overburden or deeply buried but recoverable by steam-injection methods. The reserves found in three Alberta deposits—Athabasca (40 000 km2), Cold Lake (22 000 km2), and Peace River (8 000 km2)—contain resources that could supply Canada's energy needs for more than 475 years, or total world needs for up to 15 years. With improvements in technology and commercial viability, the production potential of all the oil-sand deposits could be as high as 2.5 trillion bbl of bitumen. The Athabasca deposit, twice the size of Lake Ontario, is estimated at a minimum of 1.6 trillion bbl of bitumen in place. Extraction is not an easy process from the technological perspective, and the environmental perspective is also particularly challenging. The Athabasca oil sands are located in wetland and boreal forest ecosystems, and they are extraordinarily diverse biologically. The forest is home to more than 300 plant species, of which 42 are rare, and 10 are not found anywhere else. The boreal forest is also home to 30 species of wood warblers. The Alberta government calculates that, at today's prices using current technology, approximately 175 billion bbl of crude bitumen is economically recoverable from the three Alberta oil-sands areas. Approximately 315 billion bbl is ultimately recoverable with technological advances. Oil-laden sand may provide a bridge between the hydrocarbon era and future energy forms, so much so that oil-sands production is expected to quickly double during this second growth wave. By 2015, oil-sands production is expected to triple, which will make Canada the fifth-largest producer in the world.

Ultraviolet Degradation in Carotenoid Patches: Live Versus Museum Specimens of Wood Warblers (Parulidae)

AbstractAccurate assessment of color is essential in testing the adaptive significance of color variation in avian plumage. Over the past decade, use of objective methods for assessing color has increased, with particular emphasis on ultraviolet (UV) wavelengths. Researchers have used various source materials, most notably museum specimens, to extend or represent color measurements of individuals in natural populations. Here, we address whether the colors seen in museum specimens accurately represent the colors seen in natural populations. We focus on UV wavelengths and carotenoid-derived colors across 10 species of wood-warblers (Parulidae). Our results indicate an uneven decrease in brightness across the color spectrum, with greater relative decrease in shorter wavelengths in museum specimens. That decrease leads to differences in both hue and chroma between living and museum specimens. The difference from live specimens appears to increase with the museum specimen's age. Our results suggest that caution is needed when using data from museum specimens to test hypotheses on plumage coloration, particularly those involving communication.Degradación Ultravioleta en Parches de Carotenoides: Especímenes Vivos versus Especímenes de Museo de Especies de la Familia Parulidae

ULTRAVIOLET DEGRADATION IN CAROTENOID PATCHES: LIVE VERSUS MUSEUM SPECIMENS OF WOOD WARBLERS (PARULIDAE)

Accurate assessment of color is essential in testing the adaptive significance of color variation in avian plumage. Over the past decade, use of objective methods for assessing color has increased, with particular emphasis on ultraviolet (UV) wavelengths. Researchers have used various source materials, most notably museum specimens, to extend or represent color measurements of individuals in natural populations. Here, we address whether the colors seen in museum specimens accurately represent the colors seen in natural populations. We focus on UV wavelengths and carotenoid-derived colors across 10 species of wood-warblers (Parulidae). Our results indicate an uneven decrease in brightness across the color spectrum, with greater relative decrease in shorter wavelengths in museum specimens. That decrease leads to differences in both hue and chroma between living and museum specimens. The difference from live specimens appears to increase with the museum specimen's age. Our results suggest that caution is needed when using data from museum specimens to test hypotheses on plumage coloration, particularly those involving communication. Degradación Ultravioleta en Parches de Carotenoides: Especímenes Vivos versus Especímenes de Museo de Especies de la Familia Parulidae

Implications of climate change for North American wood warblers (Parulidae)

AbstractSince 1912, Neotropical–Nearctic migrant birds may now have up to 20 fewer days to travel between Southern Illinois, where spring is arriving later, and Northern Minnesota, where spring is arriving earlier, to exploit optimal habitat conditions (expanding leaves and caterpillar activity) for refueling and breeding. As case studies of the effect of climate change on bird migration, I analyzed two long‐term data sets of arrival times for eight species of northern breeding migratory wood warblers (Parulidae) gathered over a 100 year period in east‐central Illinois (IL, USA) and a 40 year period in western Minnesota (MN, USA). Six (IL) and seven (MN) of the wood warbler species showed no significant tendency to migrate earlier in response to earlier springs in their breeding range. These results suggest that climate change may force many species of long‐distance migratory songbirds to become uncoupled in the spring from their food resources that are driven by temperature.