Reproductive parameters in relation to food supply in the whiskered tern (Chlidonias hybrida)

Abstract

It is generally accepted that breeding terns are sensitive to food supply and that their reproductive effort could be substantially affected by the availability and access to resources. In this study we examined reproductive parameters in the whiskered tern Chlidonias hybrida in relation to food supply during the courtship feeding period (food brought by males to females) over a 2-year period (2004)(2005). We also studied whether the condition of the nestlings [body condition index (BCI)] was related to a proxy of the reproductive investment of the adults (the clutch size) during a season of food shortage. Behavioural observations showed a decrease in the intensity of male courtship feeding between years (2004 > 2005), and a strong shift in the relative abundance of the two prey groups (invertebrates/fish; invertebrate prey dropped from 88.0 to 49.3%) brought by males. This change in food delivery rates did not result in a delay in laying, but there was a significant difference in mean clutch size between years (2.71 ± 0.49 eggs in 2004 and 2.05 ± 0.78 eggs in 2005) without any within-year variation in relation to the laying dates. The egg size (volume and length) was related to the year (2004 < 2005), suggesting a trade-off in the quantity and the quality of eggs between the two seasons. We also found no evidence that the investment in a large clutch affected nestling BCI in the course of the food shortage season. Since many pairs (about 60%) interrupted breeding during the incubation stage, we assumed that parents that succeeded in rearing nestlings in these conditions were probably 'high-quality' individuals. Our results therefore showed that whiskered terns are sensitive to the varying food conditions they experienced throughout the courtship period. The diversity of prey types could be a key factor in the reproductive investment of this tern species.

Males respond to female begging signals of need: a handicapping experiment in the pied flycatcher, Ficedula hypoleuca

“…Only according to the 'female nutrition' hypothesis would we expect a direct male response by either increasing (experimentally reduced female condition) or reducing (experimentally increased female condition) his provisioning rate. Both experimental approaches have provided support for the female nutrition hypothesis (reduced condition: Moreno et al 2011;improved condition: Smith et al, 1989;Paillisson et al, 2007;Wright and Cuthill 1989;1990a;1990b).…”

Do trace metals select for darker birds in urban areas? An experimental exposure to lead and zinc

“…The day it had been laid, the egg was removed from the nest, weighed and measured (three measures of eggs' maximum length and maximum width were taken, and then averaged). Egg volume was calculated as V = 0.4866 9 Length 9 (Width 2 ) (Paillisson et al, 2007). Eggs of the first, third and fifth clutches were put back in the nest to allow incubation (n = 83), whereas the others were frozen (n = 65).…”

True deception during extra‐pair courtship feeding: cheating whiskered ternChlidonias hybridafemales perform better

“…CF takes place mostly during the pre-laying and laying periods, when the females have the highest resource requirements relating to egg formation (Lack 1940, Galván andSanz 2011). In many species food provisioned by a social male is the main source of energy (Nisbet 1973, Paillisson et al 2007, Galván and Sanz 2011. Where female fitness strongly depends on food provisioning ('CF species'), non-pair males may try to trade food offered to non-pair females in return for extra pair copulations (EPCs, Mills 1994, Tryjanowski andHromada 2005) during extra pair courtship feedings (EPCFs).…”

“…Sternidae terns are a group of waterbirds in which females spend most of the pre-laying period on the nest so as to reduce energy expenditure and requirements, while their mates provide them with food (Nisbet 1973, Moore et al 2000, Paillisson et al 2007). In these species, CF before clutch completion provides a direct benefit to females and may significantly increase the fitness of both mates (Royama 1966, Nisbet 1973, 1977, Wiggins and Morris 1986, Jönsson 1997, Helfenstein et al 2003.…”

“…In these species, CF before clutch completion provides a direct benefit to females and may significantly increase the fitness of both mates (Royama 1966, Nisbet 1973, 1977, Wiggins and Morris 1986, Jönsson 1997, Helfenstein et al 2003. Egg volume, offspring quality and survival is often correlated with the amount of food delivered by males (Nisbet 1973, Paillisson et al 2007).…”