21244420
not annotated - annotated - LINNAEUS only
Constraints on host choice: why do parasitic birds rarely exploit some common potential hosts?
1. Why are some common and apparently suitable resources avoided by potential users? This interesting ecological and evolutionary conundrum is vividly illustrated by obligate brood parasites. Parasitic birds lay their eggs into nests of a wide range of host species, including many rare ones, but do not parasitize some commonly co-occurring potential hosts. 2. Attempts to explain the absence of parasitism in common potential hosts are limited and typically focused on single-factor explanations while ignoring other potential factors. We tested why thrushes Turdus spp. are extremely rarely parasitized by common cuckoos Cuculus canorus despite breeding commonly in sympatry and building the most conspicuous nests among forest-breeding passerines. 3. No single examined factor explained cuckoo avoidance of thrushes. Life-history traits of all six European thrush species and the 10 most frequently used cuckoo hosts in Europe were similar except body/egg size, nest design and nestling diet. 4. Experiments (n = 1211) in several populations across Europe showed that host defences at egg-laying and incubation stages did not account for the lack of cuckoo parasitism in thrushes. However, cross-fostering experiments disclosed that various factors during the nestling period prevent cuckoos from successfully parasitizing thrushes. Specifically, in some thrush species, the nest cup design forced cuckoo chicks to compete with host chicks with fatal consequences for the parasite. Other species were reluctant to care even for lone cuckoo chicks. 5. Importantly, in an apparently phylogenetically homogenous group of hosts, there were interspecific differences in factors responsible for the absence of cuckoo parasitism. 6. This study highlights the importance of considering multiple potential factors and their interactions for understanding absence of parasitism in potential hosts of parasitic birds. In the present study, comparative and experimental procedures are integrated, which represent a novel approach that should prove useful for the understanding of interspecific ecological relationships in general.
Ann file
T1 Species 706 720 common cuckoos
N1 Reference T1 Taxonomy:55661
T2 Species 721 736 Cuculus canorus
N2 Reference T2 Taxonomy:55661
T3 Species 888 894 cuckoo
N3 Reference T3 Taxonomy:55661
T4 Species 1005 1011 cuckoo
N4 Reference T4 Taxonomy:55661
T5 Species 1251 1257 cuckoo
N5 Reference T5 Taxonomy:55661
T6 Species 1385 1392 cuckoos
N6 Reference T6 Taxonomy:55661
T7 Species 1499 1505 cuckoo
N7 Reference T7 Taxonomy:55661
T8 Species 1634 1640 cuckoo
N8 Reference T8 Taxonomy:55661
T9 Species 1805 1811 cuckoo
N9 Reference T9 Taxonomy:55661