Seasonal variation in weight, body measurements and condition of free-living Teal

Fox, Anthony D.; King, Roy; Watkin, J. E.

doi:10.1080/00063659209477099

Cited by 29 publications

(25 citation statements)

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“…While body weight and linear body measurements are usually used for phenotypic characterization; body conformation type and meatiness of the ducks could better be assessed using massiveness, stockiness, long-leggedness and condition index. These principal selection indices state the ratio of measurements that characterizes the proportionality of bird's body (Fox et al, 1992;Oblakova, 2007). Massiveness and stockiness which, are used to assess musculature development, are traits for solidity of the body and clearly defined traits for meat-type ducks.…”

Section: Resultsmentioning

confidence: 99%

“…The body parts measured were, body length (BDL), length between the tip of the Rostrum maxillare (bill) and that of the Cauda (tail, without feathers); breast circumference (BTC), taken under the wings at the edge of the sternum; thigh circumference (THC), measured as the circumference of the drumstick at the coxa region; bill length (BLL), measured as distance from the rectal apterium to the maxillary nail; neck length (NKL), distance between the occipital condyle and the cephalic borders of the coracoids; foot length (FTL), distance from the shank joint to the extremity of the Digitus pedis; total leg length (TLL), taken as the length of the femur, shank and metatarsal; wing length (WNL), taken from the shoulder joint to the extremity of the terminal phalanx, digit 111; massiveness (MAS) (the ratio of live body weight to body length × 100); stockiness (STK) (the ratio of breast circumference to body length × 100); longleggedness (LLN) (the ratio of total leg length to body length × 100) and condition index (CND) (the ratio of live body weight to wing length × 100). The anatomical reference points were as earlier described (Fox et al, 1992;Oblakova, 2007;Teguai et al, 2008). A 5-kg measuring scale was used for the weight measurement.…”

Section: Traits Measuredmentioning

confidence: 99%

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Discriminant analysis of sexual dimorphism in morphological traits of African Muscovy ducks

Yakubu

2011

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SUMMARYSexual dimorphism was examined in 221 randomly selected adult African Muscovy ducks extensively reared in north central Nigeria using univariate and multivariate measures of body size and skeletal proportions. The body parameters investigated included body weight, 8 primary linear body measurements [breast circumference (BTC), thigh circumference (THC), body length (BDL), bill length (BLL), neck length (NKL),foot length (FTL), total leg length (TLL) and wing length (WNL)] and 4 morphological indices (massiveness, stockiness, long-leggedness and condition index). The univariate analysis showed male dominance (p<0.05) in all the morphometric measurements, with the exception of stockiness and longleggedness where significantly higher mean values were recorded for females. Low, moderate and high positive and negative correlations among the body size and shape characters of the ducks were recorded. The canonical discriminant analysis on body weight and primary linear body measurements revealed that wing length was the most discriminating variable between the sexes, followed by body weight, neck circumference, total leg length, body length and foot length respectively. Three other variables not qualified to enter the model were expunged. The single discriminant function obtained (D= -3.116 + 0.280WNL+ 0.921BWT + 0.191NKL -0.196TLL -0.063BDL -0.283FTL) correctly classified 91.4% of individuals of known-sex ducks. This might aid in ecological studies, conservation and improvement of the indigenous ducks. RESUMENSe estudió el dimorfismo sexual en 221 patos, Muscovy Africanos, adultos, seleccionados al azar, explotados extensivamente en la región norte centro de Nigeria, empleando para ello medidas uni y multivariadas del tamaño corporal y proporciones del esqueleto. Los parámetros corporales investigados incluyeron: peso corporal, ocho medidas lineales corporales (circunferencia de la pechuga, BTC; circunferencia del muslo, THC; longitud del cuerpo, BDL; longitud del pico, BLL; longitud del cuello, NKL; longitud del pie, FTL; longitud total de la pata, TLL y longitud del ala, WNL) y cuatro índices morfológicos (masividad, solidez, largura de la pata e índice de condición). El análisis univariado mostró la dominancia del macho (p<0,05) en todas las medidas morfométricas, salvo para solidez y largura de la pata en los que se registraron valores medios significativamente más altos para las hembras. Correlaciones positivas y negativas, bajas, moderadas o altas, fueron encontradas entre tamaño corporal y caracteres morfológicos de los patos. El análisis discriminante canónico para el peso corporal y medidas lineales primarias del cuerpo, reveló que la longitud del ala fue la variable más discriminante entre sexos, seguida del peso corporal, circunferencia del cuello, longitud total de la pata, longitud del cuerpo y longitud del pie respectivamente. Otras tres variables no cualificadas para entrar en el modelo fueron eliminadas. La función discriminante simple obtenida (D= -3,116 + 0,280WNL+ 0,921BWT + 0,191NKL -0,196TL...

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Section: Resultsmentioning

confidence: 99%

Section: Traits Measuredmentioning

confidence: 99%

Discriminant analysis of sexual dimorphism in morphological traits of African Muscovy ducks

Yakubu

2011

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“…Residual indices should therefore be calculated separately for different sexes and age classes where possible. Wing length and other plumage characters should be used as BSIs with particular caution, because these are particularly plastic characters that may covary with season (Rising and Somers 1989, Ormerod and Tyler 1990, Fox et al 1992) and may not be independent of condition (Pehrsson 1987).…”

Section: Assumptions About the Relationship Betweenmentioning

confidence: 99%

Mass/Length Residuals: Measures of Body Condition or Generators of Spurious Results?

Green

2001

Ecology

383

515

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In studies of animal ecology, it is fashionable to use the residuals from an ordinary least squares (OLS) linear regression of body mass against a linear measure of size (the body size indicator, BSI) as an index of body condition. These residual indices are used to study the relationship between condition and reproductive investment, survivorship, habitat use, and other parameters. I identify a series of key assumptions underlying the use of this method, each of which is likely to be violated in some or all studies. These assumptions are: (1) that the functional relationship between mass and BSI is linear; (2) that condition is independent of BSI length; (3) that BSI length accurately indicates structural size; (4) that there is no correlation between the size of BSI relative to other structural components (i.e., shape) and the parameter against which the residuals are analyzed; (5) that BSI length is strictly independent of mass; and (6) that BSI length is not subjected to error. Violations of these assumptions place the results of some studies in question and explain the poor relationship observed between OLS residuals and more direct measures of condition.I use avian morphometric data to illustrate how OLS methods can easily lead to Type I and Type II errors through violations of assumptions (5) and (6). Significant relationships reported between OLS residual indices and parameters correlating with body size (e.g., size of sexual ornaments or egg size) are at particular risk of being spurious when the correlation coefficient between mass and BSI is low. Residual indices of condition are often likely to be more reliable when calculated with alternative methods such as nonparametric or model II regression. However, whatever the method used to produce them, residual indices are not suitable for studying the heritability of condition.

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“…However, that environmental factors strongly affect duck body condition is not a new finding; as in most migratory birds, migration events are associated with body mass and body composition changes (e.g. Clark 1979;McLandress and Raveling 1981;Ebbinge and Spaans 1995) and, even within the winter season, duck body condition is known to vary strongly because of changes in behaviour, especially the need to spend extended periods of time in courtship display to form pairs (Baldassarre et al 1986;Fox et al 1992;Tamisier et al 1995;Guillemain et al 2005b;Rhodes et al 2006;Moon and Haukos 2009). Ducks are particularly sensitive to changes in environmental conditions such as weather fluctuations (Lebreton 1973;Ridgill and Fox 1990), which likely explain the inter-annual variations in body condition recorded here.…”

Section: Body Conditionmentioning

confidence: 99%

“…Following Green et al (2011), day of recapture was included as a second-order polynomial so as to allow for potential non-linear patterns of changes across the wintering season, e.g. the known seasonal changes in body condition over the winter, generally leading to body mass being maximum in mid-winter and minimum in early and late winter (Fox et al 1992;Guillemain et al 2005b). To reduce colinearity between day and day 2 (Legendre and Legendre 1998), 1 January was considered as day 0, days from August to December being considered as negative values.…”

Section: Models and Hypothesesmentioning

confidence: 99%

Individual quality persists between years: individuals retain body condition from one winter to the next in Teal

et al. 2013

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Few studies have considered how body condition changes over time in individual birds, and most of these concerned long-lived breeding birds. We used a large database of Common Teal Anas crecca ringed and recaptured while wintering in the Camargue to study interannual persistence in wing length and body condition. Winter body condition may be a major determinant of survival during that season, and may further be related to breeding success. Indices of condition were compared for individual Teal between the moments of ringing and of recapture the following winter, analyzing each sex and age class (adult or juvenile) separately. Wing length was highly repeatable between years, though some limited annual variation was also recorded in adult males. Using scaled mass index as an index of body condition, we observed that condition at ringing was the strongest predictor of body condition at recapture for males and juvenile females, although inter-and intra-annual variation was also significant in most cases. The value of the slope for the relationship between individual body condition indices at ringing and recapture did not differ from 1 for males and for adults, whereas, for juvenile females, the slope was significantly greater than 1, indicating that individual differences in condition became more exaggerated over time. When analyses were repeated using crude body mass instead of a condition index, results were generally similar. Birds recaptured the following winter had a greater body condition at ringing that those that were not recaptured, supporting the hypothesis of a link between winter body condition and return probability. Our results demonstrate the importance of a head start in Teal, given persistent effects of obtaining better condition in the first winter, and suggest specific age and sex effects. They also underline the value of condition indices as a long-term predictor of individual quality in birds, even during the non-breeding season and for such a relatively short-lived species.Keywords Scaled mass index Á Inter-annual changes Á Body size Á Fitness Á Inter-annual persistence Zusammenfassung Individuelle Qualität bleibt von Jahr zu Jahr bestehen: Krickenten behalten ihre individuelle Körperkondition von einem Winter zum nächsten bei Es gibt nur wenige Studien zu zeitlichen Veränderungen der Körperkondition von Vogelindividuen; die meisten von diesen Untersuchungen betreffen zudem langlebige Vogelarten zur Brutzeit. Anhand einer großen Datenmenge von Krickenten Anas crecca, die in ihrem Winterquartier in der Camargue beringt und wiedergefangen wurden, untersuchten wir die Persistenz von Flügellänge und Körperkondition von einem Jahr zum anderen. Die winterliche Körperkon-dition kann einen Hauptüberlebensfaktor zu dieser Jahreszeit darstellen und darüber hinaus mit dem Bruterfolg

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Seasonal variation in weight, body measurements and condition of free-living Teal

Cited by 29 publications

References 13 publications

Discriminant analysis of sexual dimorphism in morphological traits of African Muscovy ducks

Discriminant analysis of sexual dimorphism in morphological traits of African Muscovy ducks

Mass/Length Residuals: Measures of Body Condition or Generators of Spurious Results?

Individual quality persists between years: individuals retain body condition from one winter to the next in Teal

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