1. We tested for costs of chick rearing in the black-legged kittiwake
Rissa tridactyla (Linnaeus) by removing entire clutches from 149 of 40
5 randomly selected nests, in which one or both mates was colour-bande
d. After the manipulation, we monitored adult nest attendance and body
condition at unmanipulated and manipulated nests, and measured the su
rvival and fecundity of these adults the following year. 2. Late in th
e chick-rearing period, adults from unmanipulated nests (i.e. with chi
cks) went on significantly longer foraging trips, and were significant
ly lighter for their size, than adults from manipulated nests (i.e. wi
thout chicks). 3. Adults from unmanipulated nests also survived to the
following nesting season at a significantly lower rate than those fro
m the manipulated nests (0.898 vs. 0.953), suggesting that attempting
to raise chicks can reduce life expectancy by 55%. 4. There was a tend
ency for adults from nests that were unmanipulated in year one to have
lower reproductive success in year two, primarily because of reduced
hedging success, and a higher incidence of non-breeding. 5. These find
ings suggest that mass loss in kittiwakes during chick rearing may not
be adaptive. Raising chicks can lead to reproductive costs, and the c
ausal mechanism appears to be a reduction in body condition. 6. We com
pare our results with previous brood (or clutch) size manipulation exp
eriments that have measured adult body condition, survival and/or futu
re fecundity. Although the empirical evidence suggests that long-lived
species are more likely to experience survival costs than short-lived
species, we believe the opposite may be true. We suggest that shiftin
g the experimental protocol of cost of reproduction studies from brood
enlargements (an approach taken in most prior studies) to brood reduc
tions will provide more accurate quantifications of naturally occurrin
g costs. 7. The cost of reproduction is one mechanism proposed to expl
ain the reduced survival rates reported for kittiwake populations in t
he North Atlantic relative to those in the North Pacific ocean. Oceano
graphic data, however, suggest that lower food availability may limit
survival of kittiwakes in the North Atlantic where a deeper mixed laye
r and reduced primary production combine to make conditions less favou
rable for this seabird during the winter months.