Bimodal habitat use in brood parasitic Common Cuckoos (Cuculus canorus) revealed by GPS telemetry

Attila Fülöp,Judit Bereczki,Csaba Moskát,Márk E Hauber,Miklós Bán

doi:10.1093/auk/uky019

Abstract

Abstract Obligate brood parasitic birds have evolved a rare avian strategy for reproduction by laying eggs in the nests of other species. In doing so, their breeding ranges, but not necessarily their foraging habitats, have become intimately related to the nesting territories of their hosts. We studied home range sizes and distribution patterns in Common Cuckoos (Cuculus canorus) on their breeding grounds in central Hungary, where cuckoos parasitize only Great Reed Warblers (Acrocephalus arundinaceus) in channel-side reed-beds at a high frequency (>50%). The geographic coordinates of tagged cuckoos were monitored by high-precision, remotely downloadable non-Platform Terminal Transmitter global positioning system (GPS) loggers, attached to 9 females and 6 males. Our results revealed bimodal use of habitat patches: (1) the home ranges of male and female cuckoos were packed densely along the channels where the hosts breed, and their distribution maps had high overlaps between sexes; (2) ~71% of cuckoos also visited nearby woodland patches, presumably for foraging, where the host species was not present. The size of cuckoo home ranges varied to an unusually great extent: 0.3–185 km2 as calculated by the minimum convex polygon method (85%), or 1–17 km2 when calculated by the more suitable kernel density estimation (KDE) method (Utilization Distribution 85%) for patchy habitats. Male and female cuckoos had similar home range sizes as estimated by the KDE method, consisting of 1–4 areas within the 2 habitat types of channel reed-beds and woodlands. No preference was revealed for night roosting locations between the 2 habitats or sexes. Female cuckoos were more likely to use reed-beds in the afternoons, when females parasitize host nests. Remote downloadable GPS methods offer an effective way of tracking cuckoos across large areas, but the estimation of home range sizes requires caution due to this species’ patchy and disconnected habitat use.

Highlights

In obligate avian brood parasitism, parasitic eggs are incubated and offspring are attended by a different host species (Davies 2000, Soler 2017)
Home ranges of brood parasites are expected to be related to the distribution of critical resources required for reproduction, for foraging, and other potential habitat uses relevant for other functions
Moderate (>50) or large sample sizes of locations seemed to be efficient in home range size and modality estimations, as the number of fixes used for the estimation of home ranges correlated neither with home range sizes calculated by kernel density estimation (KDE) (UD 85%) method (Table 2; Spearman’s rho = 0.21, P = 0.54, n = 11), nor with the number of separate patches used (Spearman’s rho = –0.15, P = 0.67, n = 11)

Summary

Introduction

In obligate avian brood parasitism, parasitic eggs are incubated and offspring are attended by a different host species (Davies 2000, Soler 2017). Avian brood parasites lay eggs in many host nests. The Common Cuckoo (Cuculus canorus) lays about 10–20 eggs annually (Wyllie 1981); typically each is deposited into a different nest of predominantly the same host species (Moskát et al 2009). Home ranges of brood parasites are expected to be related to the distribution of critical resources required for reproduction (the location, density and timing of host nesting attempts: Moskat et al 2006), for foraging (especially for specialists, such as many cuckoo species feeding on hairy caterpillars: Löhr 1979, Wyllie 1981), and other potential habitat uses relevant for other functions (e.g., mating areas and roosting sites: Nakamura and Miyazawa 1997)

Methods

Results

Conclusion