How climate change might influence the starvation–predation risk trade-off response

Abstract

Climate change within the UK will affect winter starvation risk because higher temperatures reduce energy budgets and are likely to increase the quality of the foraging environment. Mass regulation in birds is a consequence of the starvation -predation risk trade-off: decreasing starvation risk because of climate change should decrease mass, but this will be countered by the effects of predation risk, because high predation risk has a negative effect on mass when foraging conditions are poor and a positive effect on mass when foraging conditions are good. We tested whether mass regulation in great tits (Parus major) across the UK was related to temporal changes in starvation risk (winter temperature 1995 -2005) and spatial changes in predation risk (sparrowhawk Accipiter nisus abundance). As predicted, great tits carried less mass during later, warmer, winters, demonstrating that starvation risk overall has decreased. Also, the effects of predation risk interacted with the effects of temperature (as an index of foraging conditions), so that in colder winters higher sparrowhawk abundance led to lower mass, whereas in warmer, later, winters higher sparrowhawk abundance led to higher mass. Mass regulation in a small bird species may therefore provide an index of how environmental change is affecting the foraging environment.

The impact of increased food availability on survival of a long‐distance migratory bird

“…Changes in late-breeding-season food availability due to changes in climate, land-use, or management could therefore affect body condition of juvenile wheatears. This could affect the quality of post-juvenile molt (Dawson et al 2000), starvation risk on Fair Isle, predator avoidance behavior due to the need for increased risk taking under conditions of nutritional stress (Cresswell et al 2009), and the rate and extent of fat and muscle accumulation for autumn migration (Bairlein and Hu¨ppop 2004).…”

Thermal, food and vegetation effects on winter bird species richness of Mediterranean oakwoods

“…On the other hand, food availability is critical for winter survival of birds (Fretwell 1972;Newton 1980), throughout its influence on the satisfaction of energy demands, on building up body reserves to overcome fasting periods (e.g., the long winter night or during cold spells ;Blem 1990;Biebach 1996), and on breeding performance the following spring (Robb et al 2008). Cresswell et al (2009) have shown that the increase of 6.5°C from 1995 to 2005 in mean daily winter temperature decreased the starvation risk of great tits in England (birds responded to this scenario decreasing their body mass), while Rogers and Reed (2003) showed how the groundfeeding finch Junco hyemalis maximizes winter survival probability by integrating multiple environmental factors affecting starvation risk including temperature (but also snowfall frequency and food availability). Cresswell et al (2009) have shown that the increase of 6.5°C from 1995 to 2005 in mean daily winter temperature decreased the starvation risk of great tits in England (birds responded to this scenario decreasing their body mass), while Rogers and Reed (2003) showed how the groundfeeding finch Junco hyemalis maximizes winter survival probability by integrating multiple environmental factors affecting starvation risk including temperature (but also snowfall frequency and food availability).…”

Testing Mechanisms of Bergmann’s Rule: Phenotypic Decline but No Genetic Change in Body Size in Three Passerine Bird Populations

“…Two other studies of great tits have also reported a temporal decline in adult body mass, with decreases of 0.036 g/year over the period 1968-2002 and 0.023 residual g/year (Cresswell et al 2009). In comparison, the decrease in adult body mass found here was between 0.013 and 0.015 g/year.…”