The Auk最新文献

{"title":"Wildfires and mass effects of dispersal disrupt the local uniformity of type I songs of Hermit Warblers in California","authors":"B. Furnas, R. H. Landers, R. Bowie","doi":"10.1093/auk/ukaa031","DOIUrl":"https://doi.org/10.1093/auk/ukaa031","url":null,"abstract":"ABSTRACT Hermit Warblers (Setophaga occidentalis) sing a formulaic, type I song to attract mates, in contrast to a repertoire of more complex, type II songs to defend territories. A single, dominant type I song, or a low diversity of type I songs, often occur within a geographic area. We provide the first comprehensive description of Hermit Warbler type I song variants throughout California, USA. We recorded type I songs from 1,588 males across 101 study sites in the state from April through July 2009–2014. Using those locations and a pre-existing range map of the species, we created a maximum entropy-based breeding habitat suitability map and classified the songs into 35 variants using a typological rubric. We validated consistent classification of songs for 87.5% of the birds. We then modeled the effects of recent fire history at the local scale (10 yr, 315 km2), the amount of breeding habitat at the regional scale (8,000 km2), and the distance between territories to examine factors involved in song sameness at the local scale. We found that the probability of different birds singing the same form declined with the amount of local fire, regional habitat, and distance, and that these findings were robust to uncertainty in our song classification rubric. Using a longitudinal analysis including additional data from 10 study areas revisited in 2019, we showed that song structure within forms had drifted since our initial visits 5–10 yr earlier, and that the evenness (e.g., Simpson's measure) of song forms increased at locations that had been burned by wildfire between visits. Taken together, the results suggest that wildfires and the mass effects of dispersal of birds singing rival song forms disrupt the uniformity of type I songs locally. The results demonstrate how species traits, such as birdsong, can be used to disentangle the ecological processes that regulate observed patterns in biodiversity. Further investigation is recommended to determine whether song pattern dynamics reflect underlying genetic differences and habitat specializations among subpopulations. LAY SUMMARY The diversity of song dialects sung by Hermit Warblers in California forests is influenced by fire history. After exhaustive surveys of >1,500 birds, we mapped the distribution of 35 song dialects throughout the state. Our results suggest that differences among these songs were generated as an epiphenomenon of different subpopulations specializing on different forest types. Dispersal due to fire, and the mass effects of birds from surrounding forests, likely disrupts the uniformity of song dialects within locations, thereby promoting dynamic diversity over the longer term.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"137 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130644520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Divergence in plumage, voice, and morphology indicates speciation in Rufous-capped Warblers (Basileuterus rufifrons)","authors":"A. Demko, J. Sosa-López, Richard K. Simpson, S. Doucet, D. Mennill","doi":"10.1093/auk/ukaa029","DOIUrl":"https://doi.org/10.1093/auk/ukaa029","url":null,"abstract":"ABSTRACT The biodiversity of the Neotropics is considerable, but it is likely underestimated owing to gaps in sampling effort and a focus on using morphological features of animals to determine species differences rather than divergence in their mating signals and behavior. Recent multi-trait analyses incorporating morphological, plumage, and vocal data have allowed for more accurate quantification of tropical biodiversity. We present a comprehensive study of morphological features, plumage, and vocalizations of the Neotropical resident Rufous-capped Warbler (Basileuterus rufifrons). This species' taxonomic status is controversial because the B. r. salvini subspecies is intermediate in plumage coloration between the neighboring B. r. delattrii and B. r. rufifrons subspecies. Using morphological and spectral plumage measurements of field and museum specimens, as well as analyses of vocalizations from field recordings and sound libraries, we compared phenotypes of all 8 currently recognized Rufous-capped Warbler subspecies, with an emphasis on delattrii, rufifrons, and salvini. We found that delattrii and rufifrons differ significantly in morphology and plumage, and that salvini is similar to rufifrons in morphology and some plumage features. Vocalizations fall into 2 distinct groups, delattrii and rufifrons-salvini, which differ in multiple spectro-temporal characteristics with no overlap between them, even among individuals in the delattrii–rufifrons zone of sympatry. Our results therefore suggest that Rufous-capped Warblers comprise 2 distinct groups: Rufous-capped Warblers (B. r. rufifrons and salvini as well as B. r. caudatus, dugesi, and jouyi) and Chestnut-capped Warblers (B. r. delattrii as well as B. r. actuosus and mesochrysus). Future genomic analysis of samples from multiple sites in Mexico and Central America will further refine our assessment of range-wide phenotypic and genetic divergence in this species complex. LAY SUMMARY The taxonomy of Rufous-capped Warblers is controversial: 8 subspecies exhibit divergent plumage color and songs and consequently they are sometimes treated as 2 separate species. Using field data, museum specimens, and sound archives, we compared the body size, plumage color, and songs of all 8 Rufous-capped Warbler subspecies Seven of 8 subspecies comprised 2 groups with different color, songs, and body size: the northern, white-bellied rufifrons group and the southern, yellow-bellied delattrii group. The eighth subspecies, salvini, showed similarity to the rufifrons group, rather than being intermediate between the 2 groups as described in previous studies. We found that Rufous-capped Warblers comprise 2 separate groups, which improves our knowledge of Neotropical avian biodiversity.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133276253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Breeding performance of Common Terns (Sterna hirundo) does not decline among older age classes","authors":"I. Nisbet, D. Iles, Andrew Kaneb, C. Mostello, S. Jenouvrier","doi":"10.1093/auk/ukaa022","DOIUrl":"https://doi.org/10.1093/auk/ukaa022","url":null,"abstract":"ABSTRACT Declines in reproductive performance among older age classes have been reported in many bird and mammal species, and are commonly presented as demonstrating reproductive senescence. However, no declines in performance could be demonstrated in studies of several bird species. We measured reproductive performance in Common Terns (Sterna hirundo) of known age (2–28 yr) during a 19-yr period at a site in Buzzards Bay, Massachusetts, USA. We measured 6 components of reproductive performance and used generalized additive mixed models (GAMMs) in a Bayesian framework to analyze dependence of each measure on parental age, while controlling for variations among years and indices of individual quality. Four measures of performance improved (earlier laying date, higher values of clutch size, fledging success, and productivity) with age, most rapidly between ages 2 and 10 yr; egg mass and hatching success varied only slightly with age. No measure of performance showed reversals among the older age classes; fledging success and productivity continued to increase through at least age 22 yr. These findings are consistent with results from an earlier study of the same species. Continued increase in reproductive performance through the oldest age classes is not incompatible with “reproductive senescence” (decline in physiological or other functions required for successful reproduction) if either reproductive effort or efficiency continue to increase. Studies within our population have yielded no evidence for age-related increase in reproductive effort, but 3 studies have suggested that older Common Terns can raise chicks more successfully than younger birds without increasing reproductive effort, probably by more efficient foraging and chick provisioning. Our findings suggest that Common Terns offset reproductive senescence by continuing to improve efficiency through at least age 22 yr. Age-related changes in efficiency should be investigated in other species with similar life-history traits. LAY SUMMARY We studied Common Terns (Sterna hirundo) at a breeding colony in Massachusetts from 1970 until 2003: we banded chicks when they hatched so that we could determine their age when they returned to breed at the same site in subsequent years. The terns' breeding success continued to improve with age throughout their lives and was still increasing among birds that were 22 years old. Common Terns continually improve their skills at finding fish and provisioning their chicks, even after 20 years of practice.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115874630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Black-capped Chickadees (Poecile atricapillus) can identify individual females by their fee-bee songs","authors":"C. Montenegro, William D. Service, E. Scully, Shannon K. Mischler, Kimberley A. Campbell, C. Sturdy","doi":"10.1093/auk/ukaa028","DOIUrl":"https://doi.org/10.1093/auk/ukaa028","url":null,"abstract":"ABSTRACT Individual recognition is a social behavior that occurs in many bird species. A bird's ability to discriminate among familiar and unfamiliar conspecifics is critical to avoid wasting resources such as time and energy during social interactions. Black-capped Chickadees (Poecile atricapillus) are able to discriminate individual female and male chick-a-dee calls, potentially male and female tseet calls, and male fee-bee songs. In the current study, we used an operant discrimination go/no-go paradigm to determine whether female and male chickadees could discriminate between fee-bee songs produced by individual female chickadees as well as test which song component(s) enable this discrimination. Birds trained on natural categories—the songs of different females—learned to respond to rewarded stimuli more quickly than birds trained on random groupings of female songs and were able to transfer this learning to new songs from the same categories. Chickadees were also able to generalize their responding when exposed to the bee note of the fee-bee song of rewarded individuals; they did not generalize to fee notes. Our results provide evidence that Black-capped Chickadees can use female-produced fee-bee songs for individual recognition. However, the acoustic features underlying individual recognition require further investigation. LAY SUMMARY The current study used an operant conditioning paradigm to test whether Black-capped Chickadees can distinguish between the songs of individual female Black-capped Chickadees. Research on female song in Black-capped Chickadees has shown that female song differs from male song in sound and perception, and chickadees can distinguish between male and female song. We found that male and female chickadees can distinguish between females by listening to their song, and can do so using the whole song and only part of the song. A chickadee's ability to distinguish song by sex as well as by the individual female suggests that female song does serve a function in Black-capped Chickadees.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133221679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contributions to The History of North American Ornithology, Volume IV","authors":"Charles Walcott","doi":"10.1093/auk/ukaa025","DOIUrl":"https://doi.org/10.1093/auk/ukaa025","url":null,"abstract":"","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"51 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131305509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Estimating egg mass–body mass relationships in birds","authors":"J. Rotenberry, Priya Balasubramaniam","doi":"10.1093/auk/ukaa019","DOIUrl":"https://doi.org/10.1093/auk/ukaa019","url":null,"abstract":"ABSTRACT The mass of a bird's egg is a critical attribute of the species' life history and represents a fundamental component of reproductive effort. Indeed, the tradeoff between the number of eggs in a clutch and clutch mass lies at the heart of understanding how environmental attributes such as nest predation or adult mortality influence reproductive investment. However, egg masses have not been reported for the majority of avian species. We capitalized on the strong allometric relationship between avian body mass and egg mass to produce egg mass estimates for over 5,500 species previously lacking such information. These estimates are accompanied by measures of the robustness of the regressions used to produce them (e.g., sample size, root mean square error [RMSE] of estimation, coefficient of determination, and degree of extrapolation), thus allowing independent evaluation of the suitability of any estimate to address a particular research question relating to avian life history. Most estimates (∼5,000) were based on family-level egg mass–body mass regressions, with the remainder derived from other relationships such as ordinal regressions. We compared estimating regressions based on adult vs. female body masses and, after finding little difference between the 2, based our final estimates on adult masses as those were more numerous in the literature. What small differences between adult- and female-based regressions that did occur were not related to sexual size dimorphism across families. These new estimates, coupled with ∼5,000 egg masses reported in the literature, provide a foundation of over 10,000 species for wider investigations assessing variation in reproductive effort in birds over a broad array of ecological and evolutionary contexts. LAY SUMMARY The mass of a bird's egg is a critical attribute of the species' life history but has not been reported for the majority of avian species. We capitalized on the strong statistical relationship between egg mass and avian body mass (known for almost all bird species) to produce new egg mass estimates for over 5,500 species previously lacking such information. Most estimates (∼5,000) were based on family level regressions of egg mass on body mass, with the remainder derived from other relationships such as order regressions. We found little difference between egg mass relationships calculated from adult vs. female-only body masses and based our final estimates on adult masses as those were more numerous in the literature. These new estimates, coupled with ∼5,000 egg masses reported in the literature, provide a foundation of over 10,000 species for wider investigations examiniing variation in reproductive effort in birds over a broad array of ecological and evolutionary contexts.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121901561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Does habitat partitioning by sympatric plovers affect nest survival?","authors":"Kelly S. Overduijn, C. Handel, A. Powell","doi":"10.1093/auk/ukaa018","DOIUrl":"https://doi.org/10.1093/auk/ukaa018","url":null,"abstract":"ABSTRACT The vertical structure and composition of vegetation can influence the quantity and quality of potential nesting sites for birds. Interspecific competition for high-quality nesting habitat may force some individuals into suboptimal habitat and lead to reduced reproductive success, eventually leading to changes in distribution or abundance. Large climate-mediated shifts in vegetation, including the rapid expansion of shrubs onto tundra, are occurring in the Arctic across important breeding grounds of many shorebird species of conservation concern. We investigated effects of vegetation structure and composition on nest-site selection and nest success of sympatrically breeding American Golden-Plovers (Pluvialis dominica) and Pacific Golden-Plovers (P. fulva), which nest along an elevational gradient ranging from coastal tundra meadows to alpine tundra. Both species strongly selected nest sites with less cover of tall shrubs and other tall vegetation than available at random sites within their territories. American Golden-Plovers selected territories and nest sites that were higher in elevation and had more rocky substrates and less graminoid vegetation than those selected by Pacific Golden-Plovers. The daily nest survival rate was equivalent in the 2 species (0.966, 95% CI: 0.955, 0.975) and similar to that found in other Arctic-breeding shorebirds; however, contrary to predictions, nest survival was not associated with habitat features selected for nest sites for either species. Strong selection of open habitat for nest sites suggests that continued climate-related shrub expansion may reduce the amount of suitable breeding habitat for both species, but partitioning along the elevational gradient and differences in body size suggest that impacts may be more severe for Pacific Golden-Plovers. Additional research is needed to determine if differential selection of nesting habitat is related to survival of the adults or their young.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"137 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129624485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An early Oligocene stem Galbulae (jacamars and puffbirds) from southern France, and the position of the Paleogene family Sylphornithidae","authors":"Anaïs Duhamel, Christopher Balme, Stéphane Legal, Ségolène Riamon, A. Louchart","doi":"10.1093/auk/ukaa023","DOIUrl":"https://doi.org/10.1093/auk/ukaa023","url":null,"abstract":"ABSTRACT Together, puffbirds (Bucconidae) and jacamars (Galbulidae) form the suborder Galbulae, sister group of all other Piciformes. Hitherto, the Galbulae had no ascertained pre-Pleistocene fossil record, and all previous alleged candidates have been refuted, except possibly the Sylphornithidae. Here we describe a wing of a tiny fossil bird from the early Oligocene of the Luberon region (southern France), which we assign to the Galbulae, as a new genus and species. Several characters, especially of the ulna and wing phalanx 1 of digit II, exclude the Passeriformes and Zygodactylidae, and indicate a representative of the Piciformes. Among Piciformes, absence of papillae remigales caudales and several characters of the wing phalanx 1 of digit II make it possible to assign the fossil to the Galbulae, and exclude all other clades. The fossil Sylphornithidae, with the carpometacarpus of Sylphornis being available, show some similarity with the Luberon fossil. The combination of features of the wing elements leads to the placement of the new fossil as stem Galbulae, and tentatively within the family Sylphornithidae. As such, it fills a gap and permits to better assign the whole enigmatic tiny sylphornithids, otherwise essentially known from leg bones. This yields the first firm pre-Pleistocene fossil record for the Galbulae. Today, both the Bucconidae and Galbulidae live exclusively in tropical America. The presence of stem Galbulae in the Oligocene of Europe, and probably the late Eocene, is a new example of a present-day Neotropical clade that had stem representatives in the Paleogene of Europe. LAY SUMMARY A new fossil bird, named Jacamatia luberonensis, found in France and aged 30 myr, is the first pre-Pleistocene fossil for the whole suborder Galbulae (jacamars and puffbirds). The evolution of the total group Galbulae, now an exclusively tropical American clade, involved the Old World. Tentative placement of Jacamatia luberonensis in the fossil family Sylphornithidae helps to clarify the position of the latter enigmatic group of tiny, long-legged piciform birds.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130577254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Testing the simple and complex versions of Gloger's rule in the Variable Antshrike (Thamnophilus caerulescens, Thamnophilidae)","authors":"Rafael S. Marcondes, K. F. Stryjewski, R. T. Brumfield","doi":"10.1093/auk/ukaa026","DOIUrl":"https://doi.org/10.1093/auk/ukaa026","url":null,"abstract":"ABSTRACT Gloger's rule is a classic ecogeographical principle that, in its simplest version, predicts animals should be darker in warmer and wetter climates. In a rarely tested more complex version, it also predicts animals should be more rufous in warmer and drier climates. The Variable Antshrike (Thamnophilus caerulescens) is a widely distributed South American passerine that presents an impressive amount of plumage color variation and occupies a wide variety of climatic conditions. Moreover, genetic and vocal evidence indicate ongoing hybridization in south-central Bolivia among 3 populations with very distinct plumages. We collected color data from 232 specimens from throughout this species' distribution to test the predictions of Gloger's rule. We found a negative correlation between brightness and precipitation, consistent with the simple version of Gloger's rule. In contrast, we found that birds were darker in cooler climates, contrary to the simple version of Gloger's rule, but consistent with recent findings in other taxa. We found support for both predictions of the complex Gloger's rule and suggest it might be driven by background matching. We conclude by concurring with a recent suggestion that the simple version of Gloger's rule should be reformulated exclusively in terms of humidity. LAY SUMMARY Almost 200 years ago, the German naturalist Constantin Gloger predicted that birds that live in warm and rainy areas tend to be darker than those that in live in cool and dry areas. He also predicted that birds tend to be browner when they live in dry areas. This pattern has come to be known as Gloger's rule. South America has the world's greatest bird diversity, but Gloger's rule has almost never been studied in South American birds. This is an important question to address because it can help us learn about how species evolve respond to their environments. It becomes even more important in our era of human-induced climatic changes. We studied Gloger's rule in the aptly named Variable Antshrike. This small South American bird species varies geographically in color from almost all black to almost all white. We used a technique called reflectance spectrophotometry, which allows us to precisely quantify the colors of feathers. We measured over 200 specimens kept in natural history collections. The majority of those specimens were collected by one of us (Brumfield) in Bolivia in the early 2000s. This is the largest sample size ever used to study Gloger's rule in a tropical bird. As predicted by Gloger, we found that the Variable Antshrike tends to be darker in rainier areas, and it tends to be browner in drier and warmer areas. But contrary to Gloger's ideas, we found that it tends to be darker in cooler, not warmer, areas. We suggest that this might be because being dark in cooler places helps birds maintain warm body temperatures. We also suggest that being brown in dry areas helps the birds camouflage amidst sparse vegetation.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"1896 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130059519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The shape of avian eggs: Assessment of a novel metric for quantifying eggshell conicality","authors":"I. R. Hays, I. Ljubičić, M. Hauber","doi":"10.1093/auk/ukaa021","DOIUrl":"https://doi.org/10.1093/auk/ukaa021","url":null,"abstract":"ABSTRACT Studying the avian egg, its shape, and other aspects of its morphology, has recently undergone a renaissance. Yet most studies rely solely on 2, albeit multicomponent, metrics for the quantification of egg shape: elongation and asymmetry. The difficulty of quantifying an additional trait, the curvature, of an eggshell has yielded many attempts, including several with complex equations or spatial modeling techniques based on digitized images. Yet most of these approaches have lacked an independent single-variable metric, hampering comparative studies especially. We propose a metric for one common quality of egg shape, conicality, which is notably variable across different species' calcareous shells, including shorebirds and non-avian theropods. This metric utilizes multiple measurements of the slope along an egg's profile to produce a distribution of angular measurements, which can be analyzed with a kurtosis value. We tested this metric with sets of computer-generated and 3-dimensional-printed egg forms, where elongation, the percentage of conicality, and the relative curvature of the shell profile were systematically manipulated. For applicability to natural eggs and their diversity across taxa, the kurtosis value was used to quantify the gradient of conicality across a focal avian family, Alcidae, where the extreme ranges of kurtosis values successfully identified eggs qualitatively described as most conical in previous studies. Given the significance of egg morphology and profile curvature to eggshells' structural integrity, surface area-to-volume ratio, mobility/stability, nesting behavior, embryonic development, and individual recognition, our proposed measure of conicality could prove a useful variable to the study of avian and non-avian egg-producing species. LAY SUMMARY Avian eggs are shaped in diverse ways and the form of bird's eggshell can be influenced by its nesting requirements, parenting strategies and flight abilities. Most previous studies used only 2 metrics to study avian egg shape: (1) the width-to-length ratio and (2) the position along its length where the widest part of the egg is located (asymmetry). We propose a novel metric (conicality) for quantifying how straight/curved the profile of an eggshell is between its outermost dimensions by assessing how much either half of the profile resembles a cone. The novel conicality measure was also applied to a group of closely related birds with eggs that ranged from more elliptical to more conical. This new conicality metric successfully predicted the relative level of curvature known from casual observations of each species, which supports the method's validity.","PeriodicalId":382448,"journal":{"name":"The Auk","volume":"137 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129632773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}