Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact helpdesk@bioone.org with any questions.
Genetic variation and phylogeographic studies have been crucial for understanding mechanisms of speciation. We analyzed genetic variation and phylogeography to reconstruct the demographic history of the Rivoli's Hummingbird (Eugenes fulgens) species complex and also evaluated their morphological differentiation. This widely distributed species inhabits the highlands of Mexico and northern Central America, with 2 subspecies separated by the Isthmus of Tehuantepec (west: E. f. fulgens, east: E. f. viridiceps). We surveyed genetic variation in 2 mitochondrial DNA markers (mtDNA, with 129 individuals) and nuclear DNA (6 microsatellites, with 85 individuals). We also inferred the demographic history, estimated divergence times, and analyzed morphological variation using 470 vouchered specimens. We modeled the current potential distribution of the species using ecological niche modeling and projected it into the past to model the effects of the Pleistocene climatic cycles. Haplotype networks, pairwise FST comparisons, AMOVA, and morphological analysis revealed differences between geographically isolated populations separated by the Isthmus of Tehuantepec (IT; corresponding to the 2 recognized subspecies: fulgens and viridiceps), and by the Motagua-Polochic-Jocotán (MPJ) system fault. Demographic scenarios revealed a contraction in distribution during the last interglacial, and expansion during the Last Glacial Maximum (LGM) with little change since the LGM. Divergence between groups separated by the Isthmus of Tehuantepec ∼59,600 yr ago occurred in the presence of gene flow, suggesting that the Isthmus of Tehuantepec is a semipermeable barrier to gene flow. STRUCTURE analyses of microsatellite data detected 3 genetically differentiated groups. Several results fit a model of recent lineage divergence, including a significant signal of genetic differentiation, demographic expansion, decreased gene flow from past to present, and northward expansion during the LGM and contraction during the interglacial periods. We conclude that the genetic differentiation of E. fulgens in the Madrean Pine-Oak Woodlands resulted from recent geographical isolation of populations separated by natural barriers (IT and MPJ).
LAY SUMMARY
The present work allowed us to reconstruct the phylogeographic pattern and evolutionary history of Eugenes fulgens in the highlands of Mesoamerica.
It revealed the presence of 3 main lineages: populations west of the Isthmus of Tehuantepec (E. fulgens) and 2 populations east of the isthmus (E. viridiceps), geographically isolated from each other by the Isthmus of Tehuantepec and by the Motagua-Polochic-Jocotán system fault.
Our results support the hypothesis that the divergence and demographic expansion within the E. fulgens species complex are associated with the Pleistocene glacial–interglacial cycles.
SPECIAL FEATURE: ADVANCES IN NEOTROPICAL ORNITHOLOGY
Although the migration ecology of birds breeding in the Neotropics is still poorly studied relative to that of their counterparts breeding at north-temperate latitudes, studies conducted over the last 2 decades have revealed that migration in the Neotropics is much more common and diverse than previously thought. These studies have identified dozens of species that migrate latitudinally within South America, altitudinally within various mountain ranges, to and between Caribbean islands, and longitudinally across diverse ecosystems such as the Amazon rainforest. Advances in miniaturized tracking technologies, enormous citizen science databases, and powerful analytical approaches provide an unprecedented ability to detect and evaluate temporally and spatially fine-scale patterns, greatly facilitating the study of migratory patterns across tropical regions. We argue that a renewed effort in research on short- and long-distance bird migration within the Neotropics will allow (1) comparative studies that identify the emergent properties of migratory behavior, (2) identification of the convergent or unique mechanistic drivers of migration across diverse ecological settings, (3) formulation of effective conservation and management plans for migratory Neotropical birds, and (4) predictions about how migratory birds will respond to large-scale climatic changes within the Neotropics. Here, we review the current state of knowledge on Neotropical bird migration, with a focus on South America. We specifically examine similarities and differences in the observed migratory patterns of birds that breed in the Nearctic compared to the Neotropics and highlight key future research questions.
Miguel Ângelo Marini, Linnea Hall, John Bates, Frank D. Steinheimer, Robert McGowan, Luis Fábio Silveira, Darío A. Lijtmaer, Pablo Luis Tubaro, Sergio Córdoba-Córdoba, Anita Gamauf, Harold F. Greeney, Manuel Schweizer, Pepijn Kamminga, Alice Cibois, Laurent Vallotton, Douglas Russell, Scott K. Robinson, Paul R. Sweet, Sylke Frahnert, René Corado, Neander Marcel Heming
The ∼1.97 million egg sets (∼5 million eggs) housed in museums have not been used in proportion to their availability. We highlight the wide variety of scientific disciplines that have used egg collections and the geographic locations and sizes of these collections, to increase awareness of the importance of egg collections, improve their visibility to the scientific community, and suggest that they offer a wealth of data covering large spatial scales and long time series for broad investigations into avian biology. We provide a brief history of egg collections and an updated list of museums/institutions with egg collections worldwide. We also review the limitations, challenges, and management of egg collections, and summarize recent literature based on historical and recent museum egg materials.
Lay summary
The 5 million bird eggs in museum collections are an invaluable and underused resource that could be used for a variety of studies.
We describe briefly the history of eggs that were collected worldwide over the last 200 years.
We show that eggs from collections can be used to study ecology, behavior, evolution, classification, and species conservation.
Several of the 300 institutions with egg collections that we list are already making them digitally available and physically accessible to scientists and the general public.
We hope with this commentary to increase awareness of the importance of egg collections and improve their visibility and support.
Hybrid zones are powerful natural settings for investigating how birds diversify into distinct species. Here we present the first genomic-scale exploration of the Baltimore (Icterus galbula) and Bullock's (I. bullockii) oriole hybrid zone, which is notable for its long history of study and for its prominence in debates about avian species concepts and species limits. We used a reduced-representation sequencing approach to generate a panel of 3,067 genetic markers for 297 orioles sampled along the Platte River, a natural west-to-east transect across the hybrid zone. We then explored patterns of hybridization and introgression by comparing variation in genomic and plumage traits. We found that hybridization remains prevalent in this area, with nearly all orioles within the hybrid zone showing some degree of genomic mixing, and 41% assigned as recent-generation (F1/F2) hybrids. The center and width of the genomic and plumage gradients are concordant and coincident, supporting our finding that classically scored plumage traits are an accurate predictor of pure vs. hybrid genotypes. We find additional support for previous suggestions that the center of this hybrid zone has moved westward since it was first intensively sampled in the 1950s, but that this westward movement had slowed or ceased by the 1970s. Considered in concert, these results support previous inferences that some form of ongoing selection is counteracting the potential homogenization of these orioles via hybridization, thereby supporting their continued taxonomic separation as distinct species.
LAY SUMMARY
Hybridization between Baltimore and Bullock's Orioles has long captivated biologists and birders alike.
Along the river valleys that cross the Great Plains, hybridization is common, leading to debates about whether these are really 2 different oriole species.
We sequenced thousands of locations in the oriole genome to discover how much invisible genetic mixing is occurring in this area.
Where the species' ranges overlap, many orioles are indeed hybrids, and their combination of plumage traits is a good predictor of their genetic ancestry.
Yet the zone of hybridization remains narrow, suggesting that hybridization is a bit of a dead end, and adding to the evidence that these orioles are not blending together into a single species.
Migratory shorebirds (Charadrii) show a strong dichotomy in their breeding and wintering strategies: Arctic-breeding species typically spend the wintering season in marine habitats, while more southerly breeding species tend to do so in freshwater habitats where pathogens and parasites, particularly vector-borne blood parasites, are generally more abundant. Thus, it has been hypothesized that the former group may reduce their investment in immunity, but experimental data supporting this hypothesis are lacking. Moreover, whether this contrasting habitat selection can shape investments in immunocompetence among populations within a species is uncertain. We experimentally tested the hypothesis that there is a significant association between habitat occupancy and the strength of a pro-inflammatory immune response in the Dunlin (Calidris alpina), a widely distributed long-distance migratory shorebird that breeds in (sub-)arctic areas and winters mainly, but not exclusively, in coastal habitats. Overwintering Dunlins occupying inland freshwater and marine habitats at a similar latitude were captured and acclimated under identical conditions in outdoor aviaries. After an acclimation period, they were challenged with phytohemagglutinin to assess the pro-inflammatory immune response and its associated energetic costs, measured by basal metabolic rate (BMR) and body mass changes. We found that freshwater Dunlins exhibited a higher (63%) pro-inflammatory immune response than marine Dunlins. Although this difference did not involve significant BMR changes, the time course of body mass response differed between freshwater and marine individuals. Our findings point to the existence of different pro-inflammatory immune responses and body mass adjustments associated with the wintering habitat. These intraspecific differences are likely due to population adaptation rather than phenotypic plasticity, where not only disease risk but also physiological adaptations to different salinity levels could play an important role.
Lay summary
• Shorebird species wintering in marine habitats may experience a decreased risk of parasite infection and thus invest less in immunity than freshwater-wintering ones.
• We performed an experiment with Dunlins from marine and freshwater habitats to test this prediction at the population level.
• After a month in captivity under the same freshwater regime, birds from the marine population showed a lower immune response than those from the freshwater population.
• Such within-species differences in immunity are likely due to population adaptation to habitats posing different disease risks and osmoregulatory demands.
Brood parasitism results in substantial costs to hosts, yet not all species eject foreign eggs. Because the costs of mistakenly ejecting one's own eggs are high, selection may favor ejection behavior only if it is unlikely a host will incorrectly eject her own eggs. Eastern Bluebirds (Sialia sialis) are currently subject to relatively low levels of interspecific brood parasitism but still sometimes eject parasitic eggs. Therefore, we tested which visual cues they use to eject foreign eggs with the prediction that only the most dissimilar eggs would be ejected, reducing the likelihood of a female making a mistake. House Sparrows (Passer domesticus), which occasionally parasitize bluebirds, lay eggs that have an off-white ground color with brown speckling. Therefore, to test which colors or patterns allow for discrimination of parasitic eggs, we generated 3-dimensional (3D)-printed model House Sparrow eggs and painted them entirely off-white, entirely brown, half off-white and half brown, or off-white with brown speckling. We then sequentially placed these 4 different model eggs in the nests of Eastern Bluebirds, with each nest receiving all treatments over the course of 4 days. After watching females enter and leave the nest box just one time after placement of the model egg, we found that speckled eggs were ejected half the time (7 of 14 nests), while no other treatment was ejected more than 3 times. Thus, Eastern Bluebird females eject eggs based primarily on color patterning (i.e. a speckled pattern) rather than coloration per se, and that they can do so quickly, as the average female had removed the model egg within 6 min of entering the nest. Because Eastern Bluebirds do not lay speckled eggs, but some brood parasites do (e.g., House Sparrows, Brown-headed Cowbirds [Molothrus ater]), selection may specifically favor ejection of eggs with a speckled pattern, not just eggs that have within-egg color contrasts.
Lay Summary
Some birds (brood parasites) lay their eggs in another bird's (host's) nest; if the parasite is successful, the host ends up doing a lot of extra work raising the parasite's young.
We painted model eggs to test how Eastern Bluebirds (Sialia sialis), which lay blue eggs, figure out which eggs are theirs and which ones were laid by brood parasites.
Eastern Bluebirds rarely get rid of white, brown, or half-white/half-brown model eggs. However, they frequently eject model eggs that are white with brown spots; thus it is the spotting—and not the colors—that indicates to Eastern Bluebirds which eggs are not theirs.
SPECIAL FEATURE: ADVANCES IN NEOTROPICAL ORNITHOLOGY
Securing the long-term resilience of the world's most speciose avifauna, that of the Neotropics, requires spatially and temporally explicit data to inform decisions. We examine gaps in our knowledge of the region's avifauna through the lens of the biodiversity shortfall concept: the gaps between realized knowledge and complete knowledge. This framework serves as a useful tool to take stock of the last 25 yr of Neotropical ornithological work since the untimely death of Ted Parker. Here, we highlight 7 key shortfalls: taxonomy, distribution, abundance, evolutionary patterns, abiotic tolerances, species traits, and biotic interactions. We then propose an eighth—and new—“Parkerian” shortfall that reflects a lack of basic natural history knowledge key to understanding how species might respond to environmental challenges. Bridging this shortfall will help reverse declines by informing reintroduction, recovery network, and habitat restoration efforts. We discuss the challenges imposed by each shortfall and how strategies such as citizen-science initiatives and technological advances can either remedy or mitigate the uncertainty they generate.
Insectivorous birds reach their highest diversity in the tropics and represent a striking variety of morphological and behavioral specializations for foraging, yet explanations for these patterns are inadequate because of both our limited understanding of the drivers of ecological diversification within and among clades and of coexistence mechanisms in particular. Here we synthesize recent information on Neotropical insectivorous birds, including their diversity, evolutionary ages and locations of origin, phylogenies, and both competitive and predator–prey species interactions. We propose a novel evolutionary hypothesis for the origin and coexistence of the phenotypic diversity of insectivore foraging morphologies in species-rich communities, based on their extraordinary food-resource specializations. Specifically, we develop the Biotic Challenge Hypothesis to explain the evolution of these specializations, and we provide preliminary evidence in support of this hypothesis based on a synopsis of both Neotropical insectivore specializations by family and arthropod antipredator adaptations by category. We argue that, from the perspective of tropical insectivorous birds, and particularly in the most species-rich, mainland Neotropical communities, the environment is an arthropod desert. Coexistence with all of the other insectivores requires feeding specialization to compete exploitatively and diffusely against evolutionarily diverse species and far less frequently against sister species. The arthropod desert arises primarily because of (1) the tactical diversity of arthropod predators as insectivore competitors and (2) the evolutionary arms races involving arthropod predators with their prey, which render many arthropods inaccessible to most insectivorous predators. Our idea provides an explicit mechanism for pervasive, diffuse tropical interspecific competition, for evolutionary specialization, and for positive feedback on speciation rates at low latitudes, thereby generating new predictions and insights into tropical life histories and the Latitudinal Diversity Gradient. Other recent ideas concerning the coexistence of Neotropical insectivores, including positive species interactions within mixed species flocks, are recognized and evaluated. We discuss ways to test predictions resulting from the new view of communities developed here, including a case study of diet specialization by Costa Rican tyrannid flycatchers. Our synthesis of the origin and nature of Neotropical insectivore communities injects new life into the “zombie” idea that evolution works differently in the species-rich tropics.
LAY SUMMARY
New World tropical (Neotropical) insectivorous bird communities are extremely rich in species.
These birds are also extraordinarily diverse in how they forage, and illustrate a variety of specializations, but why?
This paper summarizes and integrates information on the evolution of the diverse Neotropical avifauna, interspecific competition, feeding specializations in the Neotropics, and arms races of insectivorous birds with insect prey, to make novel deductions and predictions.
Specifically, we propose the Biotic Challenge Hypothesis, which states that, from the perspective of many Neotropical insectivores, particularly those in lowland equatorial rainforests, food is relatively scarce, requiring specializations to find, capture, handle, and digest the prey, and requires energetic efficiency to compete effectively with other birds.
These ideas have a number of implications for life histories and for the evolution of the Latitudinal Diversity Gradient, that is, the tendency for more species to coexist at low latitudes. For example, we propose that the evolution of feeding specialization is traded off in these birds for strong dispersal ability, which has contributed to relatively high speciation rate in Neotropical birds.
The feeding specializations also have important implications for understanding a number of other aspects of Neotropical insectivorous birds, including their life histories, organization of mixed-species flocks, and their conservation vulnerability.
Following copulation, females of many seabird species spend a prolonged period of time away from the colony, building up reserves for egg formation and incubation. Here, we report that the number of sperm associated with eggs of single-egg clutch seabirds was almost an order of magnitude greater than predicted from the relationship between ovum size and sperm numbers in multi-egg clutch non-seabirds. Sperm numbers were also several times greater than the estimated number necessary for maximal fertilization success. Our results are consistent with 3 unusual features of seabird reproduction: (1) single-egg clutches, (2) prolonged sperm storage, and (3) a lag period between the end of yolk formation and ovulation. We hypothesize that sperm release from storage is under precise temporal control in these species, with high sperm numbers acting as an insurance against infertility in single-egg clutches. If true, the lag period may have evolved to provide sufficient time for sperm to be released simultaneously from storage and accumulate at the site of fertilization prior to ovulation.
LAY SUMMARY
After copulation, female birds store sperm in their reproductive systems for some time before egg production and fertilization. It is thought that sperm are gradually lost during storage, meaning that later in the storage period, if there are no further inseminations, fewer sperm should be available for insemination.
We studied the number of sperm reaching eggs in 6 seabird species, in which females spend a long time feeding at sea between mating and producing eggs.
Surprisingly, we found that the number of sperm that reached eggs in these species was much higher than expected, based on a known relationship between egg size and sperm number.
We suggest that, in these species, sperm are released simultaneously from storage just before ovulation. This may be particularly important in the species we studied, because they all lay only a single egg.
Our hypothesis implies that female birds have greater control over sperm storage and use than previously thought.
The prebasic molt is a perilous period for songbirds, characterized by heightened energetic demands and vulnerability to predators. Given these vulnerabilities, songbirds are under selective pressure to locate and use quality habitat during the prebasic molt, potentially resulting in site fidelity between years. In this study, we aimed to determine how differences in breeding and molting activity affected site fidelity for a diversity of species at the landscape scale. To accomplish our objective, we used 31 yr of banding data from northern California and southern Oregon for 16 species of songbirds with Cormack-Jolly-Seber analyses and weighted linear regression models to assess the effects of molting and breeding activity on the probability of a species returning to a site in subsequent years. Despite substantial variation in site use for breeding and/or molting, each study species had at least some locations that were used for both breeding and molting. Captured breeding birds (n = 18,574) were much more common than molting birds (n = 7,622). Breeding activity was positively correlated with higher site fidelity for 10 of the 16 species, while we found little evidence of a relationship between molting activity and site fidelity. Only the Dark-eyed Junco (Junco hyemalis) showed increased site fidelity with increased presence of molt activity. It is likely that a shifting mosaic of food resources during the post-breeding period drives dynamic movements of songbirds in search of the necessary resources to successfully complete their annual molt.
LAY SUMMARY
Birds rely on a myriad of food resources and habitats to reproduce and successfully complete their annual molt.
We used long-term capture data to assess how 16 species of songbirds varied their use of different habitats during the breeding and molting seasons in northern California and southern Oregon.
Additionally, we determined how breeding and molting activities influenced the chance of an individual returning to a site year after year.
While breeding increased an individual's chance of using the same site between years, we found little evidence that molt affected an individual's propensity to return to a site.
Unlike breeding territories, birds appear less likely to return to the same area to molt year after year. This flexibility is likely necessary to locate dispersed and unpredictable food resources during the molting season.
Eggshell pigmentation is generated by 2 major pigments, biliverdin and protoporphyrin. The latter is mostly deposited in red, brown, and black egg spots and it has been hypothesized that greater expression of egg spottiness (as measured by the number, area, and coloration of spots) may act as an honest signal of female quality for males (sexual signaling hypothesis, SSH). The important assumption of the SSH is that eggshell pigmentation correlates with phenotypic and genetic components of female quality, although phenotypic quality of females may also be under environmental control. The aim of this study was to test for the associations of protoporphyrin-based egg pigmentation with both phenotypic and genetic female traits and environmental variables (microhabitat and urbanization) in a common rallid species, the Eurasian Coot (Fulica atra). We found that the total number of egg spots was positively associated with female condition (size-corrected body mass) and expression of a putative bare-part ornament (frontal shield). The same measure of spottiness negatively correlated with the level of physiological stress in females. No evidence was found for associations between egg spottiness and genetic traits in females (neutral heterozygosity and polymorphism of pathogen recognition receptors, the Major Histocompatibility Complex), but there was a linear increase in the expression of egg spottiness over the breeding season, which may suggest that it is regulated by food availability. Our study indicates that protoporphyrin-based pigmentation of eggs reflects female phenotypic traits (condition, stress, and ornament expression) in the Eurasian Coot, although it remains to be established whether it plays any signaling role and whether it is driven by sexual selection in this species.
LAY SUMMARY
There is equivocal support for direct associations between maternal quality and deposition of protoporphyrin pigmentation (dark spots and blotches) in avian eggshells.
Research on protoporphyrin eggshell pigmentation has primarily focused on a single avian order (Passeriformes).
We examined associations of protoporphyrin-based eggshell pigmentation with female phenotypic and genetic traits in a non-passerine species, the Eurasian Coot.
Deposition of protoporphyrin in eggshells (total number per area of egg spots) positively correlated with female condition and expression of a putative bare-part ornament (frontal shield), while it was negatively associated with the level of physiological stress.
Protoporphyrin-based eggshell pigmentation acts as a reliable signal of female phenotypic (but not genetic) traits in the Eurasian Coot.
Signaling properties of protoporphyrin-based egg coloration are likely to largely differ between different evolutionary lineages of birds.
SPECIAL FEATURE: ADVANCES IN NEOTROPICAL ORNITHOLOGY
Haemosporidian parasites of the genera Plasmodium, Haemoproteus, and Leucocytozoon are among the best studied parasites of Neotropical birds. Here, we describe variation in haemosporidian prevalence (i.e. the proportion of infected individuals in a sampled population) in Neotropical birds. We review correlates of haemosporidian prevalence (including several avian life-history traits, climate, and season) and the population and evolutionary consequences of infection for Neotropical birds. We find that prevalence varies among avian taxonomic families, genera, and even among species within the same genus, suggesting that prevalence reflects multiple factors, some of which (e.g., avian incubation period) are associated with avian family-level variation in prevalence while others (e.g., avian abundance) are associated with variation in prevalence among closely related host species. We find few correlates of prevalence that have been consistently demonstrated across studies. Prevalence in populations of many Neotropical birds has been estimated by microscopic examination of blood smears, which affords limited opportunity for comparison with data generated by molecular methods. However, at one site in the Brazilian Cerrado for which we have data, prevalence determined by microscopy does not correlate with prevalence determined by molecular methods for Plasmodium, but the 2 data types are positively correlated for Haemoproteus. Haemosporidians have been hypothesized to play a role in avian sexual selection, and we find the prevalence of Haemoproteus to be lower in polygynous species than in socially monogamous species in the Neotropics, confirming a pattern shown previously among Nearctic birds.
LAY SUMMARY
Many Neotropical birds are infected by insect-vectored blood parasites belonging to the order Haemosporida. These haemosporidian parasites, commonly known as “avian malaria” parasites, infect bird species to varying degrees.
The proportion of birds in a population that are infected (parasite prevalence) has been related to variation in several avian traits, including length of incubation period and nesting height, climate, and other factors, but the patterns are not consistent among studies.
We review proposed causes of variation in haemosporidian prevalence and potential consequences of infection for bird populations. Haemosporidian parasites have plausibly been involved in the evolution of colorful plumage and mating systems in birds.
Here we find evidence for lower prevalence of haemosporidian infection associated with polygyny (where individual males mate with multiple females) in the Neotropics.
Avian haemosporidian parasites exert an important influence on the health and adaptive responses of Neotropical birds.
Functional diversity (FD) approaches have been increasingly used to understand ecosystem functioning in bird communities. These approaches typically rely on the assumption that species are perfectly detected in the field, despite the fact that imperfect detection represents a ubiquitous source of bias in biodiversity studies. This may be notably important in FD studies, because detection may depend on the functional traits used to compute FD metrics. However, little effort has been devoted to account for imperfect detection in FD studies, and therefore the degree to which species traits and detectability affects FD remains poorly understood. We predict that observed FD metrics may either underestimate or overestimate detection-corrected FD, because FD has multiple independent dimensions with different data properties. We assessed whether detection was related to bird traits (body mass, diet, and foraging stratum), accounting for habitat type, season, and phylogeny. We then used a multi-species occupancy model to obtain detection-corrected FD metrics (functional richness [FRic], functional evenness [FEve], and functional divergence [FDiv]), and compared observed and detection-corrected FD estimates in bird communities from east-central Argentina. Some functional types of birds (raptors and insectivores) were more easily overlooked, whereas others (seed and leaf eaters) were more easily detected. Some observed FD metrics underestimated detection-corrected FD (FRic and FDiv), whereas some others (FEve) overestimated detection-corrected FD. Both observed and detection-corrected FRic revealed differences between seasons, but not between habitat types. However, detection-corrected FEve and FDiv showed differences between seasons, contrary to observed estimates. Our results indicate that failure to account for unequal ease of detecting species can lead to erroneous estimates of FD because some functional types of birds are more easily overlooked. We outline some guidelines to help ornithologists identifying under which circumstances detection may be a concern and warn against the indiscriminate use of FD metrics without accounting for species detection.
LAY SUMMARY
Functional diversity relies on the assumption of perfect species detection, but how species traits affect detection remains poorly understood.
We compared observed and detection-corrected functional diversity in bird communities.
Some functional types of birds were more easily overlooked than others, biasing functional diversity metrics.
Bird diet represented a functional trait accounting for imperfect detection. Seed and leaf eaters were more easily detected; raptors and insectivores were more easily overlooked.
Observed functional diversity indices either underestimated or overestimated detection-corrected functional diversity metrics.
Failure to account for unequal ease of detecting species can lead to erroneous estimates of functional diversity because some functional types of birds are more easily overlooked.
KEYWORDS: absence of fault marks in juvenile plumage, fault bars, predator attacks, Sandhill Crane primary replacement, variability in extent of primary replacement
Using the patterns of fault bars in their primaries, we studied the mode of primary replacement in non-molting Lesser Sandhill Cranes (Antigone c. canadensis) salvaged from hunters in southwestern Saskatchewan. About 80% of their primaries are used for 2 yr and 20% for 3 yr. Primaries are replaced during the breeding season and are lost in synchronous blocks representing about half the primaries, suggesting that most adults probably can fly weakly during flight feather replacement. Cranes are large, aggressive birds, and this interesting, and undescribed mode of flight feather replacement seems adapted to the ability of adult cranes to defend their precocial chicks from predators. Strikingly, juvenile Sandhill Cranes showed no fault marks in their primaries, suggesting that their parents' ability to protect them shields them from the fright of predator attacks, which, in most birds, causes fault bars to be more prevalent and strongly expressed in juveniles than adults. Adults show interesting variation in the number of primaries replaced annually, which seems likely related to whether or not they are caring for chicks. Further, single primaries may or may not be replaced preferentially, suggesting sensitivity to feather function. Evaluating these observations must await field studies of molting adults.
LAY SUMMARY
Lesser Sandhill Cranes that breed in the far north replace about half of their primaries annually in a synchronous molt
This resolves 2 time period conflicts: the exponential increase with body size in the time required to molt, and the need to overlap primary molt with parental care.
Using fault marks, feather growth rates, and feather wear, we deciphered this previously unknown mode of primary replacement from a sample of non-molting birds.
Within adjacent blocks of same-age primaries, distance differences from feather tip to marker faults showed that feather pairs were usually lost within 24 hr of each other.
Cranes are big, tough birds, and synchronous loss of about half of the primaries helps parents defend young from formidable predators.
Synchronous replacement also reduces molt duration to the time required to grow the longest renewed primary, squeezing primary renewal of this far-northern breeder into the brief time window before their long southward migration.
Birds exhibit remarkable variation in plumage patterns, both within individual feathers and among plumage patches. Differences in the size, shape, and location of pigments and structural colors comprise important visual signals involved in mate choice, social signaling, camouflage, and many other functions. While ornithologists have studied plumage patterns for centuries, recent technological advances in digital image acquisition and processing have transformed pattern quantification methods, enabling comprehensive, detailed datasets of pattern phenotypes that were heretofore inaccessible. In this review, we synthesize recent and classic studies of plumage patterns at different evolutionary and organismal scales and discuss the various roles that plumage patterns play in avian biology. We dissect the role of plumage patches as signals within and among species. We also consider the evolutionary history of plumage patterns, including phylogenetic comparative studies and evolutionary developmental research of the genetic architecture underlying plumage patterns. We also survey an expanding toolbox of new methods that characterize and quantify the size, shape, and distribution of plumage patches. Finally, we provide a worked example to illustrate a potential workflow with dorsal plumage patterns among subspecies of the Horned Lark (Eremophila alpestris) in western North America. Studies of plumage patterning and coloration have played a prominent role in ornithology thus far, and recent methodological and conceptual advances have opened new avenues of research on the ecological functions and evolutionary origins of plumage patterns in birds.
LAY SUMMARY
Birds have many different plumage patterns that arise from coloration motifs within feathers as well as differences in color among body regions.
Plumage patterns play various roles in bird biology. They are involved in mate choice and territoriality, social interactions, camouflage from predators, and many other functions.
There is a rich history of detailed study on plumage patterns, which we review and synthesize in this manuscript.
Recent advances in photography and image processing algorithms have opened new avenues of research on plumage patterns. These open-source methods enable efficient, repeatable, and scalable analytical pipelines.
We illustrate one possible pipeline with a worked example of geographic variation in dorsal plumage patterns among populations of Horned Lark (Eremophila alpestris) in the western United States.
Looking ahead, enhanced capacity and scalability for digital photography analyses will reveal new discoveries regarding the ecology and evolution of avian plumage patterns.
This article is only available to subscribers. It is not available for individual sale.
Access to the requested content is limited to institutions that have
purchased or subscribe to this BioOne eBook Collection. You are receiving
this notice because your organization may not have this eBook access.*
*Shibboleth/Open Athens users-please
sign in
to access your institution's subscriptions.
Additional information about institution subscriptions can be foundhere