Abstract
Apart from a few well-studied examples, there is little information regarding the life history and ecological requirements of brood parasites and their hosts in most cuckoo–host systems, particularly in tropical areas. In New Caledonia, the Fan-tailed Gerygone Gerygone flavolateralis, is the exclusive host of the Shining Bronze-cuckoo, Chalcites lucidus. Here, the arms race has escalated to the nestling stage, and both host and parasite have polymorphic (difference in skin coloration) nestlings. This is a novel system for the study of brood parasitism, but very little is known about the breeding biology of the Fan-tailed Gerygone and how this may affect the co-evolutionary interactions with the Shining Bronze-cuckoo. We monitored active nests of the Fan-tailed Gerygone during six breeding seasons, using video monitoring and direct observation. Nest attendance periods of host parents were shorter during laying than during incubation, and therefore parasitism was more likely to occur during the laying period. Cuckoos eggs were on average 2 days more developed than host eggs, and thus cuckoo nestlings usually hatched before host nestlings. Fan-tailed Gerygone nestling phenotypes had similar growth and fledging rates and their frequency did not differ between habitats, indicating no apparent trade-off with skin coloration. The precipitation regime affected predation but not the parasitism rate. The current situation in New Caledonia suggests a higher selection pressure on the parasite than on the host. Our study highlights the importance of data on the breeding biology of the host in the context of studies on brood parasitism.
Highlights
The arms race between avian brood parasites and their hosts is a major topic in behavioural ecology, because it offers an insight into co-evolutionary processes in action (Rothstein 1990; Davies 2000)
In a few Chalcites–host systems, the arms race has escalated to the nestling stage with hosts discriminating the parasite nestlings (Langmore et al 2003; Sato et al 2010a; Tokue and Ueda 2010), which in turn selects for mimicry by bronze-cuckoo nestlings (Tokue and Ueda 2010; Langmore et al 2011)
2017), but can discriminate and eject the parasite nestling from the nest (Sato et al 2010a, 2015; Tokue and Ueda 2010). This host defence strategy has been reported for the Large-billed Gerygone, G. magnirostris (Sato et al 2010a), and the Mangrove Gerygone, G. laevigaster (Tokue and Ueda 2010), from Australia, which are parasitised by the Little Bronze-cuckoo, Chalcites minutillus, and in the Fantailed Gerygone, G. flavolateralis (Sato et al 2015; Attisano et al 2018), which is parasitised by the local subspecies of the Shining Bronze-cuckoo, Chalcites lucidus layardi, in New Caledonia
Summary
The arms race between avian brood parasites and their hosts is a major topic in behavioural ecology, because it offers an insight into co-evolutionary processes in action (Rothstein 1990; Davies 2000). Gerygone species do not seem to be able to reject cuckoo eggs (Mulyani 2004; Langmore et al 2005, 2009; Gloag et al 2014; Thorogood et al.2017), but can discriminate and eject the parasite nestling from the nest (Sato et al 2010a, 2015; Tokue and Ueda 2010) This host defence strategy has been reported for the Large-billed Gerygone, G. magnirostris (Sato et al 2010a), and the Mangrove Gerygone, G. laevigaster (Tokue and Ueda 2010), from Australia, which are parasitised by the Little Bronze-cuckoo, Chalcites minutillus, and in the Fantailed Gerygone, G. flavolateralis (Sato et al 2015; Attisano et al 2018), which is parasitised by the local subspecies of the Shining Bronze-cuckoo, Chalcites lucidus layardi, in New Caledonia. Very little information is available for the Fan-tailed Gerygone from New Caledonia (Barré et al 2013)
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