ras_homer_(jeff_kew).jpg

 

 

Summary: Survival is a key demographic parameter in bird populations yet remarkably little is known about the seasonal pattern of survival. Mortality may increase as a result of breeding behaviour, harsh environmental conditions, resource limitation or any combination of these; knowing which is important for understanding the ecology of population change.

We analyse an intensive ten-year colour marking programme of European blackbirds Turdus merula to estimate seasonal and sex-specific survival rates. The annual survival rate (0.67) was similar to that produced from analyses of dead recoveries across Britain, but within year variation was significant.

Survival rates were lowest during the early part of the breeding period and highest in the autumn, but there was little difference between the sexes. Understanding this pattern of variation is important in interpreting both life-history variation and the mechanisms of population change.

Robinson, R.A., Kew, J.J. & Kew, A.J. 2010. Survival of suburban blackbirds Turdus merula varies seasonally but not by sex. Journal of Avian Biology 41: 83–87 (PDF, 113.19 KB).

How African rain affects the survival of Swallow, House Martin and Sand Martin

007503-Swallow-Moss Taylor_0.jpg

 

The BTO’s Retrapping Adults for Survival scheme is designed to monitor survival rates of species of conservation concern that are monitored relatively poorly by other forms of ringing. Here we present temporal trends in survival rates for three hirundine species, Barn Swallow Hirundo rustica, House Martin Delichon urbicum and Sand Martin Riparia riparia. Estimates of apparent survival rate were similar to those found in previous studies and were correlated with rainfall on the African wintering grounds, but not with rainfall in Britain, suggesting that overwinter food resources may be more limiting.

 

Robinson, R.A., Balmer, D.E. & Marchant, J.H. 2008. Survival rates of hirundines in relation to British and African rainfall. Ringing & Migration 24: 1–6.