Culmen Length Research Articles

Effects of Summer Feeding Area on Gosling Growth in Snow Geese

Relative growth of body parts (wing, culmen, tarsus) in young Snow Geese differed among years and among summer feeding areas only a few kilometers apart in the vicinity of the McConnell River, Northwest Territories, Canada. Gosling age was unknown at time of capture, so we expressed all differences in measured characteristics as a function of culmen length. This procedure may underestimate the magnitude of differences in growth with respect to age. Year and summer feeding area had large, independent effects on relative growth. Growth of primary feathers showed the greatest variation of measurable variables among feeding areas. We argue that the cause of most differences in relative growth was nutritional variation of vegetation. If goslings with retarded growth do not entirely catch up on fall staging areas, there may be lasting demographic effects.

Differential Growth Patterns of Nestling Brown-Headed Cowbirds and Yellow-Headed Blackbirds

-As nestlings, male Yellow-headed Blackbirds (Xanthocephalus xanthocephalus) are significantly larger than female Yellow-headed Blackbirds in several measurements, and both male and female Yellow-headed Blackbirds are significantly larger than Brown-headed Cowbirds (Molothrus ater). We investigated the mechanisms by which female Yellow-headed Blackbirds are able to survive in nests with their larger siblings and how cowbirds are able to survive in the nests of hosts much larger than themselves. Growth was monitored of nestling Yellow-headed Blackbirds and Brown-headed Cowbirds, which were experimentally cross-fostered into Yellow-headed Blackbird nests, in Boulder County, Colorado during the 1986 breeding season. Measurements were recorded for weight, tarsometatarsus length, culmen length, gape width (width of bill at loral feathering), and length of ninth (outermost) primary. Nestling weight, tarsometatarsus length, and culmen length were larger in male than female Yellow-headed Blackbirds, and larger in both male and female Yellow-headed Blackbirds than cowbirds. Gape width differed significantly between male and female Yellowheaded Blackbirds throughout much of the nestling period; gape width in both were significantly wider than that of cowbirds. However, cowbirds had a significantly larger gape relative to their weight than did male Yellow-headed Blackbirds, and female Yellow-headed Blackbirds had a significantly larger gape relative to their weight than did males of the species. The relatively larger gape may enable females to compete with larger male siblings and enable cowbirds to compete with foster siblings much larger than themselves. Additionally, feather development was faster in female Yellow-headed Blackbirds than in males and was even more accelerated in cowbird nestlings. We used museum specimens of adults to calculate proportions of adult weight attained by nestlings. Cowbirds attained a greater proportion of their adult weight and adult ninth-primary length by fledging age than did Yellow-headed Blackbirds, and female Yellow-headed Blackbirds attained a greater proportion of their adult weight and adult ninth-primary length by fledging age than did their male siblings. Received 29 October 1990, accepted 10 January 1992. GROWTH rates vary greatly among animals and, although few grow at the highest potential rate (Needham 1964), they may grow at the maximum potential rate (Ricklefs 1969). Sibling competition may be a major component in the selection for rapid growth (Werschkul and Jackson 1979) and, in some species, may result in brood reduction (Bortolotti 1986). Brood reduction may occur through siblicide (Mock 1984) or asynchronous hatching (Lack 1954, Richter 1982, Mead and Morton 1985). Among sexually dimorphic, altricial birds that also hatch asynchronously, one might expect a high degree of sibling competition resulting in a biased sex ratio. While some investigators of sexually dimorphic birds have found skewed sex ratios of nestlings or fledglings (Howe 1977, Slagsvold 1 Present address: Department of Biology, Fort Lewis College, Durango, Colorado 81301, USA. et al. 1986, Teather and Weatherhead 1989), others have reported that sex ratios were not significantly skewed (Selander 1960, Fiala 1981, Bancroft 1983, Weatherhead 1983). Interestingly, in all the above-listed studies with skewed sex ratios, the sex ratios were female-biased. Explanations for female-biased sex ratios include: depending on hatching sequence, males suffer higher mortality during food shortages (Slagsvold et al. 1986, Teather and Weatherhead 1989); and males are more costly to raise (Howe 1977, Slagsvold et al. 1986). None of the above-listed studies, however, have shown how females may compete with their larger male siblings for food. Richter (1983) reported no significant bias in sex ratios for Yellow-headed Blackbirds (Xanthocephalus xanthocephalus), a sexually dimorphic, asynchronously hatching species. He demonstrated a significant difference between nestling growth rates of males and females, but suggested that there may be little disparity in

Morphometric variability on a microgeographical scale in two inshore seabirds

The range of morphometric variation among two inshore seabirds, the Kerguelen cormorant Phalacrocorax atriceps verrucosus and the gentoo penguin Pygoscelis papua was investigated on the Kerguelen and Crozet archipelagos. Four measurements (weight, culmen, flipper and body length for gentoos; weight, culmen, wing and tarsus length for cormorants) were compared in the same seven localities on Kerguelen. In addition, culmen and wing length were compared in four localities on Crozet for gentoo penguins. The two species exhibited similar trends in variation within Kerguelen although the range of variation was greater in cormorants. Compared to the largest cormorants and gentoo of Kerguelen, the smallest stocks were 60 and 36% of the weights, respectively. There is little evidence elsewhere of similar broad morphometric variability in seabirds on a microgeographical scale. The variation observed did not follow a regular cline and appeared to be less related to physical factors (sea temperatures) than to the local biological factors during the breeding season.

Discrimination of Mallard Strains on the Basis of Morphology

We detected differences in morphology among strains of wild, urban, and game-farm mallards (Anas platyrhynchos) from the Mississippi Flyway. A 3-strain discriminant function analysis (DFA) model (to discriminate 3 strains) and a 2-strain DFA model (to discriminate wild mallards from urban mallards, the strain that most closely resembled wild mallards) were developed to predict group memberships on the basis of 6 morphological variables. We used a stepwise procedure to develop a reduced 2-strain model that discriminated wild mallards on the basis of 3 variables : tarsus width, total tarsus length, and culmen length. Accuracy of the models ranged from 87.3 to 96.4% for males and 95.7 to 100% for females. Canonical coefficients are provided for use with unstandardized measurements to classify mallards

Long-Term Decline in Body Size in a Snow Goose Population: Evidence of Environmental Degradation?

(1) The effect of environmental factors on annual body size variation was investigated in a breeding population of lesser snow geese (Anser caerulescens caerulescens L.) La Perouse Bay, Manitoba, using data from 1969 to the present. The population size has increased from approximately 2000 to 10 000 pairs during this period (Cooch et al. 1989). (2) Annual mean gosling body mass, tarsus and culmen length (measured at fledging) declined significantly by approximately 16% (240 g), 4% (3.4 mm), and 2% (0.93 mm) respectively in cohorts hatching between 1976 and 1988. The decline in gosling size has led to a significant decline in size of locally bred adults. Annual mean adult female body mass, tarsus and culmen lengths declined by approximately 15% (270 g), 6% (5.4 mm), and 4% (2.3 mm), respectively, in cohorts hatching between 1969 and 1986. (3) Gosling growth and subsequent adult size was also reduced in years with cold, wet weather after hatch. (4) The decline in gosling size was not dependent on the pattern of annual variation in egg or hatch mass, nor systematic changes in annual mean hatch date or post-hatch weather. Goslings reared by individual adult females showed a decline in size over time, suggesting that the general decline reflects a non-genetic change in gosling growth rates during the fledging period. The most probable non-genetic factor is a long-term reduction in food available to the geese at La Perouse Bay. This reduction in food availability may reflect over-exploitation of primary food plants by the geese.

Sexing great SkuasCatharacta skuaby discriminant analysis using external measurements

A discriminant function used to sex Great Skuas at Foula, Shetland correctly classified 87.5% of the sample from which it was derived, and several lines of evidence suggest that it performed similarly with a sample of live birds caught over a three‐year period. There was no evidence that any of the variables used in the analysis changed during the period of the study or were affected by conditions at the colony during birds’ development. However, this may not be the case with birds caught in future years. Culmen length was correlated with age, and so was not suitable for inclusion in the analysis. The discriminant function derived by one worker performed comparatively poorly with a sample of birds measured by a different worker, despite the fact that their measurements were in close agreement with each other. We advocate great caution in the use of discriminant functions, particularly when a function has been derived by a different worker.

Growth Rate is Negatively Correlated with Hatch Date in Black Brant

Arctic geese nest in a highly seasonal environment in which ungrazed plants reach peak nitrogen concentrations when goslings hatch (Sedinger and Raveling 1986). Grazing by geese prolongs peak nutrient concentrations but reduces food availability. This should cause nutrient availability to decline seasonally. Here, we test the hypothesis that late—hatching goslings of Black Brant (Branta bernicla nigricans) grow more slowly than those hatching early. We substracted the sizes of wild goslings from those of captive—reared goslings of the same age and regressed the differences against hatch date. Differences between wild— and captive—reared goslings for body mass, tarsus length, and culmen length were significantly negatively related to hatch date; i.e., late—hatching wild goslings were smaller than those hatching early, after accounting for age. We detected no between—year difference in gosling size, but male goslings were larger than females of the same age for all measures. Egg size was only weakly associated with size of goslings 1 mo after hatching, but we detected no effect of other brood characteristics on growth. Seasonal variation in gosling growth rate may favor early nesting in arctic geese.

Sexual Dimorphism in the Kea Nestor notabilis

Morphological differences between the sexes in Keas Nestor notabilis were quantified from a sample of 86 sexed museum specimens, nine sexed zoo captives and 129 live, wild-caught birds. The results demonstrate that Kea are sexually dimorphic. Males are about 5% larger than females in linear measurements of body size and their upper bills are on average 12-14% longer, with a slightly larger radius of curvature. The dimorphism in bill size was statistically independent of the difference in overall body size, suggesting the possibility of intersexual differences in niche utilisation. Culmen length appears to be a useful means for distinguishing sexes in the field: our data indicate an optimum separation criterion of 43.9 mm for wild-caught individuals. Culmen length measurements from specimens originating in captivity were more variable. There was no evidence that sexual dimorphism increases with sexual maturity in this species.

Influence of hatching order and brood size on growth in jackass penguins

Jackass penguins Spheniscus demersus hatch two different-sized eggs asynchronously: the second-hatched chick, being, on average, 59% of the weight of the first-hatched chick on hatching. We examined the effect of hatching order on growth rates of mass, culmen length and culmen depth by comparing: (i) growth rates of first-and second-hatched chicks, and (ii) chicks from experimentally synchronized broods to chicks from normal asynchronous broods. Only growth rates in mass showed significant variation. Within a brood, B chicks grew more slowly than A chicks. The effect of synchronizing a brood was to lower the growth rate of both chicks to that of a B chick, suggesting that equal-sized siblings feed less efficiently. Chicks hatching from larger A eggs, that had been synchronized for age and size with chicks from B eggs, did not grow faster, indicating that chicks hatching from A and B eggs do not have intrinsically different growth rates. Single-chick nests result usually from egg infertility. Singletons sh...

Morphometry, diet and habitat in the kingfishers (Aves: Alcedinidae)

Factor analysis of the linear dimensions of 92 species of kingfisher indicated that morphological differences were associated with four diet categories (aquatic, littoral, terrestrial and fossorial animals). Analysis of covariance confirmed the significance of these differences for culmen, tarsus and tail length but not for wing length. Habitat factors resulted in some significant differences but these were less easy to interpret. One case of intraspecific variation showed similar trends for culmen length.

Gender determination by body weight and linear measurements in American and Chilean flamingos, previously surgically sexed: Within‐sex comparison to greater flamingo measurements

AbstractGender was determined by laparoscopic visualization of the gonads for 38 adult American flamingos (Phoenicopterus ruber ruber L.) and 36 adult Chilean flamingos (P. chilensis L.). Concomitant body weight (kg) and linear measurements (mm) of the culmen (bill), tarsus (tarsometatarsus), middle toe, and wing were taken. Statistical comparisons of body weight and linear measurements for male vs. female were made for each species. Also, the same‐sex statistical comparisons were made between these two species, and between each of these two species and with data for greater flamingos (P. r. roseas L.) from a previous publication. As previously published for greater flamingos, an overlap between sexes existed in all measurements with males on average larger than females for both American and Chilean flamingos. However, Students' t‐test indicated a significant sexual difference for all measurements between males and females of each species except for culmen length in Chilean flamingos. Students' t‐test also indicated a significant difference when species were compared (Chilean vs. greater, and American vs. Chilean) and subspecies (American vs. greater) were compared for most of the 5 measurements. Thus, despite limitations imposed by between‐sex overlap, weights and linear measurements, especially tarsus, middle toe, and wing length, appear to be useful in determining an individual's gender when species or subspecies identification is considered.

Differences in growth parameters of Ross' Geese and Snow Geese: evidence from hybrids

Ten Ross' Geese, 14 hybrid Snow – Ross' Geese, and 4 Snow Geese were raised together at McConnell River, Northwest Territories. The birds fed on native vegetation, supplemented by dog food. Measurements taken at regular intervals of weight, tarsus length, culmen length, and culmen height were fitted to the Gompertz curve, and the three growth parameters derived therefrom were subjected to genetic analysis. Results showed that Ross' Geese had more genes contributing to a higher growth constant than Snow Geese, but little allelic dominance was observed. Snow Geese grew to a larger final size, with evidence that dominance was more important in that process. Reasons for the faster growth but smaller adult size are discussed with reference to the severity of conditions on nesting areas during the gosling period.

Estimating Carcass Fat and Protein in Northern Pintails during the Nonbreeding Season

I used northern pintails (Anas acuta) collected from August through March 1979-82 in the Sacramento Valley, California to derive equations to predict ether-extracted carcass fat, carcass protein, and skeletal lean dry weight. Ether-extracted carcass fat was best predicted by total fat depot weight (wet skin, abdominal fat, and intestinal fat) (r2 = 0.94) and estimates based on carcass water content (r2 = 0.93-0.98). Measured carcass protein was best predicted by a multiple regression including total protein depot weight (breast muscles, leg muscles, and gizzard) and tarsus length (R2 = 0.79). I predicted skeletal lean dry weight by a multiple regression incorporating culmen, tarsus, and wing length (R2 = 0.77). Predicted carcass fat agreed well with measured carcass fat in an independent data set of 30 pintails using total fat depot (r2 = 0.92-0.96) and carcass water (r2 = 0.97-0.99), but predicted carcass protein agreed less well with measured

Site Fidelity and Survival Differences between Two Groups of New World Red Knots (Calidris canutus)

Abstract During the boreal winter, New World Red Knots (Calidris canutus rufa) principally occupy two areas widely separated in latitude. The larger group of approximately 100,000 birds is distributed along the Patagonian Atlantic coast, the smaller group of about 10,000 along Florida's Gulf coast. Resightings of banded individuals showed no interchange between these groups. The annual survival rate of knots marked in Florida is twice that of marked knots that winter in Patagonia. During northward migration Florida knots were sighted significantly less often at a major New Jersey stopover site than knots marked in Argentina. Whether this segregation is maintained during the breeding season is unknown. Wing and culmen lengths did not differ between the groups. The higher survival of individuals from the smaller Florida group, which presumably migrates a much shorter distance than the Argentina birds, runs counter to current evolutionary theories on the benefits of migration.

The breeding biology of the white‐chinned petrel Procellaria aequinoctialis at South Georgia

Aspects of the breeding biology of the whitc‐chinned petrel Procellaria aequinoctialis were studied at South Georgia. Laying, hatching and fledging dates, together with egg and adult measurements, rate of weight loss of eggs and incubating adults and data on the duration of incubation shifts were recorded. Chick growth in weight, tarsus length, culmen length and wing length from hatching to fledging was followed in detail and breeding success and causes of mortality documented. Comparisons are made with other populations of the species, other members of the genus Procellaria and other Procellariiformes. Despite being the largest burrow‐nesting petrel in the world, P. aequinoctialis conforms well to the overall relationships between body weight and breeding parameters for Procellariiformes in general.

ECOLOGICAL IMPLICATIONS OF INTERCOLONY SIZE-VARIATION IN JACKASS PENGUINS

Summary Duffy, D. C. 1987. Ecological implications of intercolony size-Variation in Jackass Penguins. Ostrich 58: 54–57. The culmen length of courting adult male Jackass Penguins Spheniscus demersus varied between colonies, with the largest culmens in southern Namibia and east of Cape Point, South Africa. Taxonomic distance, a single measure combining several morphological characters, was significantly and positively correlated with geographic distance between colonies. Population changes between 1956 and 1978 were not significantly correlated with male mandible or flipper length, suggesting that adult size cannot be used as an index of population changes at individual colonies. Possible dispersal may complicate attempts to use changes at individual colonies as indices of changes in fish stocks of surrounding waters.

Body Morphometrics and Molt of Bonaparte's Gulls in the Quoddy Region, New Brunswick, Canada

In the Quoddy region of New Brunswick, Canada, the postnuptial molt and feather renewal of Bonaparte's Gulls lasted about 14 weeks with the primary feather molt of the second-year birds being more advanced than that of the adults by 20 to 30 days or 2 to 3 primary feathers. Males were larger than females by body weight, and body, culmen, and tarsal lengths. There was a general trend for migrants passing through the Quoddy region during July and August to be larger in size than during October and November. Based on culmen and tarsal lengths measured on museum specimens collected from different geographical regions of the breeding range, there was a general trend for decrease in body size from east to west, which suggests that the first migrants through the Quoddy region represented populations from the east followed later by western populations.

Fat Deposition and Usage by Arctic-Nesting Sandhill Cranes during Spring

Fat Deposition and Usage by Arctic-Nesting Sandhill Cranes during Spring

Breeding biology and population dynamics of giant petrels Macronectes at South Georgia (Aves: Procellariiformes)

The breeding biology and population dynamics of the two species of giant petrels, Macronectes halli and M. giganteus, were studied at Bird Island, South Georgia during 1978–81. The mean laying date of M. halli was in early October, five to six weeks ahead of M. giganteus. In both species males take the larger share (c. 54%) of incubation. The eggs of the two species are of the same size but in M. halli the egg formed a significantly higher proportion of the female body weight. On hatching M. giganteus chicks are 5% heavier than M. halli chicks but there are no sexual differences in weight. Brooding and guarding in M. halli is 11 days longer than in M giganteus and males undertake 60–68% of the duties during this time. Males of both species take five to six days longer to fledge than females and M. halli chicks have a seven to nine day shorter fledging period. The sex ratio amongst chicks is 1: 1.Chick growth (weight, culmen length and wing length) is summarized. Males reach higher peak and fledging weights than females in both species and have significantly larger bills through most of the fledging period. The increase in wing length was similar in both sexes until near the end of the fledging period. Adult M. halli tend to be shorter‐winged, larger‐billed and lighter in weight than M. giganteus at Bird Island.Chick mortality was on average c. 10% higher in M. giganteus than in M. halli leading to a lower overall breeding success in the former. Whilst the breeding population of M. giganteus seems to have stayed relatively stable M. halli has increased in numbers over the last 20 years. However 26‐9‐57–5% of birds colour‐ringed in 1978 did not breed in the subsequent two breeding seasons. Mean annual survival of breeding adults was c. 0–90. Breeding commenced between age 6 and 9 years with males possibly starting earlier than females. The increased population of M. halli and the better survival of their chicks is attributed to the considerable increase in breeding Antarctic fur seals Arctocephalus gazella which provide an abundance of carrion for M. halli nestlings during the first 30 days after hatching.

Phenotypic Variation of the Mexican Duck (Anas platyrhynchos diazi) in Mexico

A collection of 98 breeding Mexican Ducks (Anas platyrhynchos diazi) was made in Mexico from six areas between the United States border with Chihuahua and Lake Chapala, Jalisco, in order to study geographic variation. Plumage indices showed a relatively smooth clinal change from north to south; northern populations were most influenced by the Northern Mallard (A. p. platyrhynchos) phenotype. Most samples were fairly uniform; that from the Río Conchos area in northeastern Chihuahua was noticeably more variable than the others. Soft part coloration is described. Weights varied from 849 to 1,243 g in males and from 647 to 1,264 g in females. Measurements of total, wing, and culmen lengths and bill width were usually significantly larger in males at any one site, but showed no regular geographic trends. Hybridization between platyrhynchos and diazi phenotypes may or may not be increasing in the middle Rio Grande and Río Conchos valleys; available data are insufficient to decide. Introgression of the Northern Mallard genome into Mexican diazi populations may be largely historical owing to recent reductions in the number of migratory Mallards reaching Mexico. A spring 1978 aerial census yielded an estimate of 55,500 diazi-like birds in Mexico. Populations of diazi appear to be as large as the available habitat allows; management should be directed towards increasing and stabilizing the nesting habitat; and the stability of the zone of intergradation should be investigated.