Food Regulates Reproduction Differently in Different Habitats: Experimental Evidence in the Goshawk

Abstract

Food supplementation experiments have been widely used to get detailed insight into how food supply contributes to the reproductive performance of wild animals. Surprisingly, even though food seldom is distributed evenly in space, variation in local habitat quality has usually not been controlled for in food supplementation studies. With results from a two-year feeding experiment involving a habitat-sensitive avian top predator, the Northern Goshawk Accipiter gentilis, we show that treatment effects on goshawk reproductive performance are habitat dependent. Extra food reduced nestling mortality in low-quality territories where prime habitat (forest) is scarce, but not in high-quality territories where prime habitat is abundant. Consequently, brood size did not differ between treatment categories in heavily forested territories, but fledgling numbers differed between unfed and fed goshawk pairs breeding in territories where forest is scarce. However, because extra food was not superabundant, this artificial increase in offspring number induced a dramatic decrease in nestling condition in low-quality territories. Treatment effects were detected even after controlling statistically for other potentially confounding effects (year, territory identity) and strongly covaried with territory-specific abundances of the most important summer prey species. These results highlight the importance of acknowledging the effect that small-scale variation in habitat quality and availability of natural food may have on the results of food supplementation experiments. In order to assess the generality of food supplementation effects, the integration of habitat heterogeneity and variation in food abundance is thus needed, especially among species in which small-scale variation in habitat quality influences demographic patterns.

Competitive exclusion within the predator community influences the distribution of a threatened prey species

“…Forming an expansion of a long-term study on forest raptors (e.g., Byholm and Nikula 2007, Byholm and Kekkonen 2008, Byholm et al 2011, local flying squirrel occurrence was mapped within 150 m from 30 occupied goshawk nests and 35 Ural Owl nests in SP, and 30 goshawk nests in VS in early-mid May during 2006-2010. This scale was chosen as a rationale based on previous knowledge of landscape composition preference by flying squirrels at the patch scale (e.g., Mo¨nkko¨nen et al 1997, Hanski 1998).…”

Diet of the Little Owl (Athene noctua) during the pre-reproductive period in a semi-arid Mediterranean region

“…This can be explained by the raptor's search for high-energy food that increases body fitness and improves reproductive performance (Byholm and Kekkonen 2008;van den Burg 2009). This feeding strategy is crucial and decisive in determining breeding success and survival rate of the species under cold conditions during the winter (Massemin and Handrich 1997;Reynolds, Schoech, and Bowman 2003).…”

“…Goutner and Alivizatos 2003;Baziz et al 2005), no previous study has investigated temporal variation in the diet composition, in particular, over the pre-reproductive period of the species. It is a known fact that both quality and quantity of the food consumed during this pre-reproductive period may contribute to the breeding adult's health and fitness by affecting the performance of physiological traits (Reynolds, Schoech, and Bowman 2003;van den Burg 2009) and thus have a significant effect on the reproductive performance (clutch size, nestling feeding, food supplementation) (Byholm and Kekkonen 2008). The aims of this study are to (i) describe the diet spectrum of the Little Owl in northeastern Algeria where no previous study has been carried out, (ii) assess the composition and diversity of the diet, (iii) investigate the temporal variation in prey categories identified by analyzing pellets, and (iv) describe metric characteristics of pellets.…”

Trophic Niche and Feeding Strategy of the White Stork (Ciconia ciconia) during different Phases of the Breeding Season

“…Moreover, both quality and quantity of food during each breeding stage play a key role in the determination of parental health and fitness by affecting the performance of their physiological traits (Reynolds et al, 2003;Van den Burg, 2009). Therefore, it has a significant effect on the reproductive performance and breeding success, especially in wild species (Byholm and Kekkonen, 2008).…”