Bill Height Research Articles

Phenotypic signatures of urbanization are scale-dependent: A multi-trait study on a classic urban exploiter

Understanding at which spatial scales anthropogenic selection pressures operate most strongly is a prerequisite for efficient conservation and management of urban biodiversity. Heterogeneity in findings on the strength and direction of urbanization effects may result from a lack of consensus on which spatial scales are most adequate when studying biotic effects of urbanization. Therefore, here, using the house sparrow (Passer domesticus) as model, we test the hypothesis that more than one spatial scale will explain variation among phenotypic stress markers. By applying a unique hierarchical sampling design enabling us to differentiate between local and regional effects of urbanization, we here show that the strength and direction of relationships with the percentage of built-up area – a simple structural measure of urbanization - vary among phenotypic stress markers and across the spatial range over which urbanization is measured. While inverse relationships with scaled body mass and bill height of adult house sparrows (Passer domesticus) were strongest when the degree of urbanization was quantified at city-level, similar relationships with corticosterone concentrations in feathers were only detected at the scale of individual home ranges. In contrast, tarsus length, wing length, and two measures of feather development were not significantly related to urbanization at any spatial scale. As the suite of phenotypic stress markers applied in this study revealed signatures of urbanization over a broad spatial range, we conclude that measures aimed at mitigating impacts of urbanization on free-ranging populations should best be implemented at multiple spatial scales too.

Sexual Dimorphism and Foraging Trips of the Laysan Albatross (Phoebastria immutabilis) on Guadalupe Island.

Simple SummaryWe evaluated the existence of sexual dimorphism in Laysan albatross from Guadalupe Island. Males were larger than females across all the morphological variables analyzed. We created a sex predictor model for Laysan albatross individuals that requires a minimum number of input variables and will considerably reduce the handling times and field costs of future studies. Laysan albatross foraging trips were recorded during their breeding season over multiple years and no significant differences were found between the distances travelled by males versus females.Sexual dimorphism in the Laysan albatross (Phoebastria immutabilis) on Guadalupe Island was evaluated during the breeding seasons of 2015–2018 by measuring and comparing 10 morphological attributes: cranial length, bill length, nostril length, cranial width, bill height, bill width, tarsus length, closed wing length, opened wing length, and wingspan length in reproductive adults (n = 135). Males were larger than females across all traits (Student’s t-test, p < 0.05, p < 0.05). We created a logistic model using stepwise regression to predict sex based on morphological variables. This model indicated four significant morphological predictor variables (z < 0.05) and was able to successfully predict the sex of P. immutabilis individuals in more than 90% of the cases. Based on these predictor variables, a web app was developed to determine the sex of the Laysan albatross in the field, providing a non-invasive method for rapid data collection that reduces costs and handling times while improving conservation efforts. We tracked Laysan albatross (n = 36) during breeding seasons and found no significant differences between females and males for either trip length (GLMM, F = 0.017, DF = 1, 1, p = 0.917 > 0.05) or maximum trip distance (GLMM, F = 0.374, DF = 1, 1, p = 0.651 > 0.05). Our results suggest that both sexes show a strong preference to travel to highly productive coastal waters northeast of the breeding colony that are influenced by the California Current. The present research will serve to establish a baseline to protect this species on Guadalupe Island and highlights the importance of understanding sexual dimorphism in at-risk seabird species.

Sexual Dimorphism and Seasonal Variability of Shield Size in the Endangered Hawaiian Coot (Fulica alai)

The endangered Hawaiian Coot (Fulica alai) is one of few native waterbird species remaining in Hawaii, USA. On the island of Oahu, 56 adults were captured and sexed using a molecular method, and sexual dimorphism, seasonal variation in shield size (possibly sexually selected), and use of morphometrics to predict sex as an alternative to molecular sexing were investigated. The sex ratio was significantly male biased: 39 males, 17 females (P = 0.003). No morphometric character assessed independently differed significantly between sexes (0.056 < P < 0.975). However, a multiple regression approach indicated that tarsus length, bill height, tail length, and wing length in combination differed between sexes, but prediction of sex was nonetheless possible with only 65% accuracy. Male shield size was larger during the pre-breeding and breeding seasons than the post-breeding season, but did not vary significantly in females, the interaction between sex and season in the model being significant (P < 0.02). Within the breeding and pre-breeding seasons (a subsample of total birds), multiple regression indicated sexual dimorphism in shield width, shield length, and wing length, but prediction of sex was again only possible with 68% accuracy. Thus, neither model predicted sex sufficiently accurately for this morphometric approach to be a viable substitute for molecular sexing.

Morphometric Differences Between Sexes In the White-Faced Ibis (Plegadis chihi)

ABSTRACT Sexual dimorphism in birds may express itself as differences in body size, plumage, color and/or behavior. Many species are monomorphic in color, which makes sex determination difficult in the field. In order to develop a tool to distinguish between male and female specimens of the White-faced Ibis, Plegadis chihi, by using external body measurements, the objective of this work was to quantify morphometric differences between sexes in adults of this species. The following variables were measured: culmen length, bill height and width, tarsus length, middle toe (with claw) length, wing chord, tail length and body mass. Males were larger than females in all of these variables, and presented statistically significant differences for six out of eight parameters. Three discriminant classification functions were obtained with an accurate total classification rate in >85% of the cases. The length of the culmen, tarsus, middle toe with claw, and wing chord, were among the most useful variables to discrimi...

Sexing monomorphic western mountain greenbuls on Mount Cameroon using morphometric measurements

The western mountain greenbul, Andropadus tephrolaemus, is a poorly-known monomorphic forest greenbul. We investigated whether morphological measurements could be used to discriminate between sexes of this species, with a sample of birds captured in two forest types on Mt Cameroon. We used discriminant function analysis based on a combination of traits to develop models to discriminate between sexes. The sex of birds predicted from these models was compared with molecular sexing of the same individuals. Discriminant analysis revealed that a discriminant function incorporating wing length, tail length and bill height allowed 74% of western mountain greenbuls to be sexed correctly based on morphometric measurements alone. Sex ratios varied between montane and lowland forests, with the former having a higher proportion of males (70.5 and 54.6%, respectively), but the difference was not statistically significant. Cloacal sizes did not differ between males and females, and males do not developlarge cloacal protuberances while breeding. This is in agreement with low predicted levels of sperm competition in this species. We show that sexing based on morphology has its limitations, but can still provide some insight if DNA analysis is not available.

Sexing Monomorphic Western Mountain Greenbuls on Mount Cameroon using Morphometric Measurements

The western mountain greenbul, Andropadus tephrolaemus, is a poorly-known monomorphic forest greenbul. We investigated whether morphological measurements could be used to discriminate between sexes of this species, with a sample of birds captured in two forest types on Mt Cameroon. We used discriminant function analysis based on a combination of traits to develop models to discriminate between sexes. The sex of birds predicted from these models was compared with molecular sexing of the same individuals. Discriminant analysis revealed that a discriminant function incorporating wing length, tail length and bill height allowed 74% of western mountain greenbuls to be sexed correctly based on morphometric measurements alone. Sex ratios varied between montane and lowland forests, with the former having a higher proportion of males (70.5 and 54.6%, respectively), but the difference was not statistically significant. Cloacal sizes did not differ between males and females, and males do not develop large cloacal protuberances while breeding. This is in agreement with low predicted levels of sperm competition in this species. We show that sexing based on morphology has its limitations, but can still provide some insight if DNA analysis is not available.

Allometry as evidence of sexual selection in monochromatic birds: the case of the Coscoroba Swan (Anseriformes: Anatidae)

The Coscoroba Swan, Coscoroba coscoroba (Molina, 1782), is a poorly known aberrant Anserine endemic to South America. We captured adult birds (189 male, 157 female) from the largest population in Brazil at the Taim Ecological Reserve, State of Rio Grande do Sul, Brazil. Different patterns between sexes can reflect differences in selection, and positive allometry may indicate that a character is sexually selected. We used body weight and 10 morphological measurements to examine allometric differences between males and females of C. coscoroba. Males were consistently larger than females. Analysis of scaling relationships against body mass showed that nostril, tail, wing and bill height were positively allometric (i.e., heavier birds had relatively larger character lengths), but there were no sexual differences in allometric slopes. However, for a given mass, mature females had longer tails, longer wings (up to metacarpophalangeal articulation) and shorter heads than males. In the light of current debate in the literature, we discuss whether such positively allometric traits and sexual differences in scaling may be indicative of sexual selection. Although Coscoroba Swan is a monogamous species, increasing the size of some attributes may confer some advantage for mate selection or male-male competition and, contrary to other studies, we suggest that positively allometric slopes alone should not be considered as evidence for sexual selection of the considered traits.

The reliability of morphometric discriminant functions in determining the sex of Chilean flamingos Phoenicopterus chilensis

Abstract Monomorphic birds cannot be sexed visually and discriminant functions on the basis of external morphological variations are frequently used. Our objective was to evaluate the reliability of sex classification functions created from structural measurements of Chilean flamingos Phoenicopterus chilensis museum skins for the gender assignment of live birds. Five measurements were used to develop four discriminant functions: culmen, bill height and width, tarsus length and middle toe claw. The functions were tested on a sample of live flamingos from a zoo. The best classification for museum flamingos was given by a function using tarsus length, bill width and middle toe claw (97%). However, this function did not give the best classification for the zoo-based flamingos (81%) which had the best sex assignment by a function including measurements of tarsus, culmen and bill height and width (85%). This shows that a function giving good results in the sample from which it originated may not be as good when applied to another group of animals. Our study emphasizes the need for assessing the accuracy of a function by testing it with other methods to ensure its suitability when being applied.

Morphometric Variation and Population Relationships of Krüper's Nuthatch (Sitta krueperi) in Turkey

Abstract We studied the population relationships of Kruper's Nuthatch (Sitta krueperi) by capturing 82 individuals using mist nets in six different areas in Turkey during the breeding season, from March to June 2005–2008. Forty-one different morphometric characters were measured. Morphometric characters measured (x ¯ ± SD) were: body mass = 13.11 ± 0.88 g, wing length = 74.79 ± 2.35 mm, bill length = 17.65 ± 0.76 mm, and tarsus length = 19.10 ± 0.93 mm, respectively. A stepwise discriminant analysis of four populations retained seven statistically significant measurements: body mass, wing length, length of P 8, alula, bill height, back nail, and left nail. These analyses allowed discrimination among populations. The population in the Aladaglar Mountains differed from others even though it overlapped with the population in the Lutfi Buyuk Yildirim Research Forest, and marginally with the population at Kartalkaya Mountain. Cross validation for the other three populations confirmed large overlap in m...

Predicting the sex of the Sedge Warbler (Acrocephalus schoenobaenus) by discriminant analysis

Sexual size dimorphism was examined in 273 immature Sedge Warblers (Acrocephalus schoenobaenus) caught in northern Poland during autumn migration in 2008 and 2009. Each individual was measured (wing, tail, head to bill, bill length, bill width, bill height, two measurements of tarsus width and hind claw length) and a blood sample was taken for molecular sexing. A forward stepwise discriminant function analysis was used and three discriminant functions were proposed for sexing Sedge Warblers. The first function, ap-plied to the nine measurements, identified wing and bill length as the best measurements for sexing and correctly classified 82% of individuals. The second and third functions, ap-plied to only wing length and tail length, identified the former as the best single measure-ment, and these two correctly classified 83% and 82% individuals, respectively. These functions may be used as a tool for sexing Sedge Warblers when blood sampling is impos-sible, such as in historical ringing records. However, the functions may be valid only for young birds in north and central Europe measured by experienced ringers.

Morphological Differences of Sex and Age in the Okinawa RailGallirallus okinawae

Abstract Morphological measurements of Okinawa Rail Gallirallus okinawae were made to evaluate methods of sex determination. Males were significantly larger (P<0.05) than females for 23 of the 25 features measured. Forward discriminant function analysis identified eight of the most useful measurements as maximum wing, exposed culmen, tarsus, total head, gape, bill height, body weight and third toe length. Further analysis selected total head (TH) and bill height (BH) as the most useful variables to determine sex and produced the discriminant function: 0.467×TH+0.827× BH-53.811, which correctly identified the sex of 100% of the individuals in the data set. Bill and iris color proved useful for determining age, as did the tip shape and color of the primary feathers. Characteristics of juvenile primaries were especially useful, since the birds retain their first year plumage until molting at about one year old. Individual variation also exists, however, requiring comprehensive evaluation of all biometrics an...

Principal Component Factor Analysis of the Morphostructural Traits of Muscovy Duck

Eleven body measurements were taken on 320 adult Muscovy duck (124 male and 196 females) within the guinea savanna zone of central Nigeria. The body measurements included Body Length (BDL), Body Width (BDD), Bill Length (BLL), Bill Width (BLD) Bill Height (BLH), Shank Length (SHL), Body Height (BH), Head Length (HL) Neck Length (NL), Head Width (HD) and Wing Length (WL). Sex had significant influence on all traits with higher means recorded for male traits. The correlation coefficient of the body measurements range from negative to moderately high for both sexes. In factor solution of the principal component analysis with VARIMAX rotation of the transformation matrix, four factors with ratio variances of 71.85% were identified for male, the first factor accounted for 36.66% and had its loading for body width, bill width, shank length and body height. In female 2 factors with ratio variances of 53.04% were extracted, the first and the second factors explain 36.76 and 16.27% of the generalized variances with the first had its loading on body length, bill width, body height, neck length and wing length respectively. From the result factor loading in Muscovy duck is sex dependent and can be exploited in improvement programme for the bird.

Use of Factor Analysis Scores in Multiple Regression Model for Estimation of Body Weight from Some Body Measurement in Muscovy Duck

Factor and multiple regression analysis were carried out on morphological traits (body length, body width, bill length, bill width, bill height, shank length, body height, head length, head width, neck length, wing length, chest circumference and body weight) of male and female muscovy ducks. Obvious sexual dimorphism was exhibited between sexes, relationship between body measurement and body weight were examined through factor and multiple linear regression analysis. Three factors had positive significant effect on body weight of the male muscovy representing size and shape while only one factor had positive relationship with body weight in female, accounting for 84.2% and 63.5% of variation in body weight for male and female respectively. The result reveals that body measurements can be better selected for improvement in weight for male muscovy than for females.

Analysis of Morphological Traits of Geographically Separated Population of Indigenous Muscovy Duck (Cairina Moschata)

Inter and intra specific variation among muscovy duck ecotypes from three agroecological zones of Nigeria were studied The work evaluate the morphological variation of three ecotypes ( rainforest ecotypes, humid or guinea savanna and dry savanna ecotypes) covering southern or coastal region, central and northern part of Nigeria. Twelve morphological traits including weight were considered. Significant (p<0.05) variation exist within and between ecotypes using population coefficient of variation (ANOVA) bill height had the highest coefficient of variation 79.52 while body length recorded the least variation. There are marked differences in body morphology between sexes in all the ecotypes indicating significant sexual dimorphism. Correlation between the traits were low to high. The inter specific variations in bill structure and body morphology are indication of adaptation to the environment and influence of ecological condition

Specimen Shrinkage in Cinnamon Teal

Abstract Body size measurements from freshly collected birds and dried museum specimens were used to evaluate specimen shrinkage in Cinnamon Teal (Anas cyanoptera). Six of seven body measurements of female Cinnamon Teal differed significantly after specimen drying, whereas five of seven male body measurements differed. The largest amount of shrinkage was in bill height, bill width, and tarsus length. Bill length at nares showed no significant shrinkage suggesting it is a more conservative measurement than exposed culmen and, therefore, a more reliable method for accurately measuring bill length. Correction values for body size measurements are reported for future waterfowl studies combining measurements of both live birds and museum specimens.

Timing of Hatching and Indirect Selection on Body Size — the Impact of Bad Weather on the Great TitParus majorin Niepołomice Forest (S Poland)

Abstract. This paper reports on the case of selection, due to influence of bad weather on nestling number, acting through different pathways on breeding date and morphological traits in breeding Great Tits. Multiple regression of relative fitness on tarsus length, bill height and forearm length, revealed significant phenotypic selection on male forearm length and female bill height. However, nestling mortality during the bad weather depended on their age, which suggested breeding date as a focal trait for selection. The multiple regression analysis of relative fitness on both body traits and hatching date shows that in males only breeding date was significantly related to fitness, and selection on forearm resulted from correlation of forearm with hatching date. A similar analysis in females shows that both bill height and timing of hatching were equally related to fitness, therefore in this sex both bill height and date of hatching were focal traits for selection.

Morphometric Variation in Marbled Murrelets, Brachyramphus Marmoratus, in British Columbia

Morphometrics (culmen length, bill height, bill width, wing chord length, and tarsus length) were taken on 664 marbled murrelets at Desolation Sound and Mussel Inlet, British Columbia, during 1994 to 1997, in order to assess morphological differences within and between populations and the accuracy of a discriminant function analysis to identify the sex of birds. An assessment of interand intra-observer variability in measurements was also made. Significant inter-observer effects and some intra-observer effects were found. Data from recaptured murrelets indicated they had decreased in size with age, which was attributed to interobserver effects. Wing chord length had the highest measurement error (66.8%) among observers and tarsus length had the lowest error (36.8%). Deviations of measurements from the mean were compared among years and sites. No inter-annual differences were detected in any morphometric at Desolation Sound. Significant differences in culmen length, wing chord length, and tarsus length were found between birds from Mussel Inlet and Desolation Sound, which might indicate discrete populations. The degree of sexual dimorphism in this species was small (measurements of females average 98% of corresponding measurements of males) and discriminant function analysis revealed only about a 70% success rate in allocating birds to sex; therefore, its widespread use in this species is not recommended. Future studies of marbled murrelets, or other avian species, which involve large numbers of personnel, should incorporate extensive training of all observers, with data continually cross-checked in order to minimize intraand inter-observer differences in measurements.

Morphological Differences in Pacific Coast Populations of Greater White-Fronted Geese

We examined morphological relationships of three Pacific coast populations of Greater White-fronted Geese (Anser albifrons). Adult geese were captured and measured at three breeding areas in Alaska and two wintering areas in California, 1980-1991. A two-step discriminant function analysis examined morphological differences among the three populations. Stepwise discriminant function procedures created the simplest measurement models. Each sex was analyzed separately since multivariate analysis of variance indicated that males were significantly larger than females for all three populations. Tule Greater White-fronted Geese (A. a. gambelli) were significantly larger than Pacific Greater White-fronted Geese (A. a. frontalis), hereafter Pacific Geese. The first step of discriminant function analysis created models to differentiate Tule Geese from the Pacific Geese. Bivariate stepwise discriminant function models consisting of only two measurements correctly classified 92% of males (bill height, bill width) and 96% of females (bill height, culmen) of these subspecies. The second step of discriminant function analysis compared a small population of Pacific Geese from the Bristol Bay Lowlands (BBL) of southwestern Alaska with the large population of Pacific Geese that breed on the Yukon-Kuskokwim River Delta (YKD) of westcentral Alaska. We developed models with three (culmen, diagonal tarsus, midtoe) and five (culmen, diagonal tarsus, midtoe, total tarsus, bill height) measurements from stepwise discriminant function analyses to correctly classify 72% of males and 74% of females of these populations. Thus, morphology of Tule Geese differed highly significantly from Pacific Geese, as expected, but differences between populations from the BBL and YKD areas were also significant. Morphometric analyses as these provided supporting evidence for clinal variation in populations of Greater White-fronted Geese. They also underscore a need for further studies of differences among North American populations of Greater White-fronted Geese to resolve classification and to allow formulation of subpopulation/subspecies management strategies.

Body Condition, Food Habits, and Molt Status of Late-Wintering Ruddy Ducks in California

Body Condition, Food Habits, and Molt Status of Late-Wintering Ruddy Ducks in California

Breeding, Morphology, and Growth of the Endangered Dark-Rumped Petrel

-Dark-rumped Petrels (Pterodroma phaeopygia phaeopygia) in the Galapagos archipelago breed on several islands. Life-history characteristics such as mate and site fidelity, large egg size, long incubation periods, long incubation bouts, and chick growth patterns are similar to those of other procellarids. Adults nest annually, but the timing of breeding is out-of-phase among the islands of Floreana, Santa Cruz, and Santiago. Banding data for 1,500 adults and juveniles indicated that little or no interbreeding occurs among islands. From adult morphological characteristics measured during five years on Floreana and one year on both Santiago and Santa Cruz, we found that on Floreana, adults were sexually monomorphic in all measured characteristics except bill height, and the adults from Floreana tended to be larger in both size and mass than adults from the other two islands. The possibility that each island's population is distinct should be considered when formulating management plans concerning this species. Received 10 May 1989, accepted 6 November 1989. THE DARK-RUMPED Petrel (Pterodroma phaeopygia phaeopygia) breeds on at least four of the islands in the Galapagos archipelago: Floreana, Santa Cruz, Santiago, and San Crist6bal. They adhere to a rigid, annual breeding schedule; most other Galapagos seabirds breed semiannually or opportunistically (Harris 1977, Valle et al. 1987). Adult petrels return repeatedly to the same island-specific colonies to breed, and they probably disperse over broad areas of the eastern Pacific Ocean between breeding attempts (Murphy 1936). The Dark-rumped Petrel is endangered at all of its breeding sites (King 1981). We studied aspects of petrel breeding biology including mate and site fidelity, egg size, and adult weight loss during incubation bouts. We also compared the breeding chronologies of colonies on Floreana, Santa Cruz, and Santiago; and we examined adult morphological characteristics and chick growth from all three islands. The breeding biology of the Dark-rumped Petrel on Santa Cruz was studied previously by Harris (1970). Tomkins (1985) surveyed the archipelago in 1978-1979 and suggested that breeding was not synchronized among islands. This was supported by Coulter et al. (1981, 1982 1 Present address of author to whom reprint requests should be sent: School of Forestry and Environmental Studies, Duke University, Durham, North Carolina 27706 USA. unpubl.) who found differences in the initiation of breeding among different colonies on Floreana. We studied the breeding biology of the petrel on Floreana as a corollary to a conservation effort that alleviated petrel mortality through control of introduced mammalian predators (Cruz and Cruz 1987a, b; J. B. Cruz and F. Cruz 1987). MATERIALS AND METHODS Study areas. -We collected data from three locations in the Galapagos National Park in 1981, and 19831986 (Fig. 1). The colony on Floreana Island (1?13'S, 90?22'W) was located in a dormant volcano (Cerro Pajas) at 300-640 m above sea level (asl). We sampled petrels from the most accessible and least fragile nests along the interior walls of the volcano to minimize disturbance (J. B. Cruz and F. Cruz 1987). On Santa Cruz Island (0?9'S, 90?21'W), we sampled nests in the Media Luna colonies and their environs at 600-800 m asl. In these colonies, petrels frequently dig their burrows into the soft soil of water gullies (Harris 1970). We also studied petrels in the highlands of Santiago Island (0?8'S, 90?32'W), where colonies were widely scattered. Petrels on this island nest in small groups located in an area of at least 35 km2. We monitored ca. 25 km2. We found most nests deep in caves and other hard-to-reach areas at 500-900 m asl. Field methods.-On Floreana we checked 43 nests (1981), 104 nests (1983), and 100 nests (1984, 1985, and 1986) from January through September. We assessed nests at least weekly, but more frequent checks were made in some years. We banded all adults with 7-mm diameter num317 The Auk 107: 317-326. April 1990 This content downloaded from 157.55.39.132 on Mon, 02 Jan 2017 17:57:26 UTC All use subject to http://about.jstor.org/terms 318 CRUZ AND CRUZ [Auk, Vol. 107