Abstract
Behavioral and/or developmental plasticity is crucial for resisting the impacts of environmental stressors. We investigated the plasticity of adult foraging behavior and chick development in an offshore foraging seabird, the black noddy (Anous minutus), during two breeding seasons. The first season had anomalously high sea-surface temperatures and ‘low’ prey availability, while the second was a season of below average sea-surface temperatures and ‘normal’ food availability. During the second season, supplementary feeding of chicks was used to manipulate offspring nutritional status in order to mimic conditions of high prey availability. When sea-surface temperatures were hotter than average, provisioning rates were significantly and negatively impacted at the day-to-day scale. Adults fed chicks during this low-food season smaller meals but at the same rate as chicks in the unfed treatment the following season. Supplementary feeding of chicks during the second season also resulted in delivery of smaller meals by adults, but did not influence feeding rate. Chick begging and parental responses to cessation of food supplementation suggested smaller meals fed to artificially supplemented chicks resulted from a decrease in chick demands associated with satiation, rather than adult behavioral responses to chick condition. During periods of low prey abundance, chicks maintained structural growth while sacrificing body condition and were unable to take advantage of periods of high prey abundance by increasing growth rates. These results suggest that this species expresses limited plasticity in provisioning behavior and offspring development. Consequently, responses to future changes in sea-surface temperature and other environmental variation may be limited.
Highlights
Contemporary climate change has led to organisms encountering more extreme and variable environmental conditions [1,2]
Parents feed their chick by regurgitation, with food offered in several small batches immediately upon their return from foraging; unclaimed food is retained by the parent [28]
Foraging success decreased with increasing sea-surface temperatures (SSTs) in 2005/06, with SST negatively related to both log10 daily feeding frequency (F1,18 = 70.80, r2 = 0.797 P,0.001; Fig. 2a) and total daily meal mass (F1,18 = 24.07, r2 = 0.572 P = 0.001; Fig. 2b) provided by adults
Summary
Contemporary climate change has led to organisms encountering more extreme and variable environmental conditions [1,2]. Some studies of long-lived vertebrates with low reproductive capacity support this idea Individuals of these species that can adjust their behavior, morphology and/or physiology to changing environmental conditions have greater lifetime reproductive success [6,7,8]. The generality of such responses in all long-lived species is questionable; some breeding seabirds will, to a limited degree, adjust foraging patterns to changes in environmental conditions at the expense of their future survival [15,16]. Where such plasticity occurs it is uncertain whether it is sufficient to allow species to cope with the environmental variation they face
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