B. Faivre et al., Breeding strategy and morphological characters in an urban population of blackbirds, Turdus merula, ANIM BEHAV, 61, 2001, pp. 969-974
Pairing patterns in monogamous birds are thought to be the consequence of m
utual mate choice by males and females for characters linked to individual
quality in the opposite sex. Although this may result in assortative pairin
g for a single character, there may be no simple match between male and fem
ale phenotype if the traits linked to individual quality are sex specific.
For instance, in several passerine species, females tend to select males on
the basis of territory quality or characters that may reflect health or vi
gour, whereas males benefit from pairing with females in good condition tha
t breed early because early breeding increases reproductive success. We inv
estigated pairing patterns in an urban population of the sexually dimorphic
European blackbird in relation to bill colour in males and body condition
in females, over a 3-year period. Females breeding early were in significan
tly better condition than those breeding late. The number of breeding attem
pts per season was significantly positively correlated with female conditio
n, while the number of fledglings reared by a female in a breeding season w
as positively correlated with the number of breeding attempts, independentl
y of female condition. Bill colour varied in males and was related to body
weight, although not to condition. Female condition was correlated with mal
e bill colour within pairs, with males showing more orange bills being pair
ed to females in better condition. We discuss the observed pairing pattern
in relation to individual or territory quality and to the constraints and c
osts associated with reproduction in each sex. (C) 2001 The Association for
the Study Animal Behaviour.