Weather‐mediated decline in prey delivery rates causes food‐limitation in a top avian predator

Abstract

Inclement weather can negatively affect breeding birds directly by exposure to factors such as severe temperature and rainfall, or indirectly by reducing food supply. During a three‐year study of Arctic peregrine falcons Falco peregrinus tundrius breeding in Nunavut, Canada, we estimated annual prey density at a biologically relevant scale (i.e. the home range of breeding pairs), and examined the manner in which prey density and within‐season weather conditions influenced occupancy of breeding sites, egg‐laying, hatch rate, prey delivery rates and growth and survivability of nestlings. The first two summers of our study (2010–2011) were warm and dry, while the third summer (2012) was cool and wet, and was preceded by a severe spring rain event. We found that occupancy of breeding sites was consistently high. As a proportion of the number of eggs laid, hatch rate did not change among years, but the number of eggs laid per occupied site declined in the third year of the study. In the first two years of the study, the number of nestlings per occupied sited was high, but declined in the third year. Total prey density at the home range scale was similar in 2010 and 2012, while the highest prey density was recorded in 2011. Total prey delivery rates to nestlings and nestling growth rates were significantly lower in 2012, which received more precipitation than 2010 and 2011. Nestling growth rates were similar in 2010 and 2011, but were markedly different in 2012; for both sexes the period of rapid growth was of shorter duration in 2012 and asymptotic weights were lower. This research contributes to the growing body of evidence that indicates severe rain events and ongoing periods of wet weather can reduce reproductive output of Arctic‐breeding raptors regardless of whether it occurs during laying, incubation or brood rearing.

Maxent modeling for predicting the spatial distribution of three raptors in the Sanjiangyuan National Park, China

“…Temperature can impact animal reproduction and growth directly, and it can also indirectly affect there is relatively high temperature and relatively strong light during the day in geography. The Saker falcon was also affected by the highest temperature in December and the lowest temperature in January, meaning that the species is sensitive to extreme tem- (Fisher et al, 2015;Robinson, Franke, & Derocher, 2017), but the three species of Raptors are located in areas where precipitation is small and there is almost no extreme precipitation, so the impact on the three species is not significant. Stronger sunlight is conducive to plant photosynthesis, which affects plant production to affect phytophagous prey, thereby affecting the food supply of raptors (Hawkins et al, 2003).…”

“…Stronger sunlight is conducive to plant photosynthesis, which affects plant production to affect phytophagous prey, thereby affecting the food supply of raptors (Hawkins et al, 2003). The Saker falcon was also affected by the highest temperature in December and the lowest temperature in January, meaning that the species is sensitive to extreme tem- (Fisher et al, 2015;Robinson, Franke, & Derocher, 2017), but the three species of Raptors are located in areas where precipitation is small and there is almost no extreme precipitation, so the impact on the three species is not significant.…”

Regional and temporal variation in diet and provisioning rates suggest weather limits prey availability for an endangered raptor

“…In the case of predators that feed on moving prey, factors such as habitat or weather may reduce accessibility by modifying prey behaviour or capture probability (Elkins 1983, Schlaich et al 2015. This may create situations of food limitation despite high prey abundance (Robinson et al 2016).…”

“…In the absence of prey abundance data, an indirect way to evaluate food availability in the environment may be to assess foraging yields (the number of individual prey animals caught per unit time of hunting, e.g. Simmons 2000, Terraube et al 2011 or prey provisioning rates at nests by direct observations (Amar et al 2003, Leckie et al 2008 or using automated cameras at nests (Z arybnick a et al 2012, Schroeder et al 2013, Robinson et al 2016.…”

Multi-scale selection models predict breeding habitat for two Arctic-breeding raptor species

“…The selection of productive areas in close proximity to water by peregrine falcons and rough-legged hawks was likely linked to the availability of accessible prey (Wightman and Fuller 2005;Booms et al 2010;Coulton et al 2013). Arctic-breeding passerines and shorebirds are more abundant in well-vegetated lowlands and wetlands than in sparsely vegetated areas (Robinson et al 2014), and are a key food source for breeding peregrine falcons (Court et al 1988;L'Hérault et al 2013;Robinson et al 2017). Furthermore, the abundance and distribution of Arctic grazers such as lemmings, which are important prey for peregrine falcons (Bradley and Oliphant 1991;L'Hérault et al 2013;Robinson et al 2017) and rough-legged hawks (Potapov 1997;Bechard and Swem 2002) are also correlated with tundra productivity during summer (Rodgers and Lewis 1986;Olofsson et al 2012).…”