Individual quality, survival variation and patterns of phenotypic selection on body condition and timing of nesting in birds

Abstract

Questions about individual variation in "quality" and fitness are of great interest to evolutionary and population ecologists. Such variation can be investigated using either a random effects approach or an approach that relies on identifying observable traits that are themselves correlated with fitness components. We used the latter approach with data from 1,925 individual females of three species of ducks (tufted duck, Aythya fuligula; common pochard, Aythya ferina; northern shoveler, Anas clypeata) sampled on their breeding grounds at Engure Marsh, Latvia, for over 15 years. Based on associations with reproductive output, we selected two traits, one morphological (relative body condition) and one behavioral (relative time of nesting), that can be used to characterize individual females over their lifetimes. We then asked whether these traits were related to annual survival probabilities of nesting females. We hypothesized quadratic, rather than monotonic, relationships based loosely on ideas about the likely action of stabilizing selection on these two traits. Parameters of these relationships were estimated directly using ultrastructural models embedded within capture-recapture-band-recovery models. Results provided evidence that both traits were related to survival in the hypothesized manner. For all three species, females that tended to nest earlier than the norm exhibited the highest survival rates, but very early nesters experienced reduced survival and late nesters showed even lower survival. For shovelers, females in average body condition showed the highest survival, with lower survival rates exhibited by both heavy and light birds. For common pochard and tufted duck, the highest survival rates were associated with birds of slightly above-average condition, with somewhat lower survival for very heavy birds and much lower survival for birds in relatively poor condition. Based on results from this study and previous work on reproduction, we conclude that nest initiation date and body condition covary with both reproductive and survival components of fitness. These associations lead to a positive covariance of these two fitness components within individuals and to the conclusion that these two traits are indeed correlates of individual quality.

Costs of Reproduction in Breeding Female Mallards: Predation Risk during Incubation Drives Annual Mortality

“…In birds, reproductive costs have most commonly been measured by reductions in survival rates of breeding adults in the year immediately following experimental increases in reproductive effort (Askenmo 1979, Nur 1984, Reid 1987. Because these costs are incurred in the future, i.e., after young have been successfully raised, they imply some sort of physiological stressor that leads to increased mortality risk (Calow 1979, Blums et al 2005, Harshman and Zera 2006. However, pinpointing the precise cause and timing of such mortality has been hampered by methodologies such as annual mark-resighting data that measure survival only at a coarse annual scale.…”

Factors Affecting Timing of Breeding in the Tawny Owl

“…This seemed to be a common phenomenon in birds [11,12] but not a universal one even in the tawny owl [see 7]. Large body size in earlybreeding females was against some earlier findings [e.g.…”

“…1): 1) Being more competent in reproduction [9], older individuals might also be more competent being capable to breed earlier than younger ones [e.g. 11,12]. Birds that are smaller-sized [13,14] but heavier, and thus probably in better condition [15,16], should breed earlier than larger but lighter ones.…”

Análisis de la condición corporal de aves Passeriformes en zonas secas del norte del Alto Valle del Magdalena, Colombia

“…No obstante, al igual que otros conceptos biológicos, este término se ha definido de múltiples formas (Brown 1996), y conceptualmente se ha relacionado con el estado nutricional (Krebs y Singleton 1993) o el capital de energía acumulada en el cuerpo como resultado de la alimentación y el desgaste fisiológico cotidiano (SchulteHostedde et al 2001, 2005, Peig y Green 2009. Frecuentemente se ha propuesto que esta característica influye en aspectos como la supervivencia, la productividad, el comportamiento, el éxito reproductivo o, en suma, la eficacia biológica del individuoaptitud Darwiniana- (Brown 1996, Bachman y Widemo 1999, Bustnes et al 2002, Blums et al 2005, Peig y Green 2009, por lo cual ha sido utilizada en estudios de etología (Núñez-Cebrián et al 2011), ecología y biología de la conservación (Peig y Green 2009) de una amplia variedad de taxones, entre estos las aves.…”