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Extra-territorial forays by great tits are associated with dawn song in unexpected ways

Citation

Bircher, Nina; van Oers, Kees; Hinde, Camilla A.; Naguib, Marc (2020), Extra-territorial forays by great tits are associated with dawn song in unexpected ways, Dryad, Dataset, https://doi.org/10.5061/dryad.cvdncjt1c

Abstract

Conspicuous male signals often play an important role in both attracting mates and deterring rivals. In territorial species with extra-pair mating, female and male forays to other territories may be an important component underlying female choice and male mating success and might be influenced by male advertisement signals. Yet, whether off-territory foraying is associated with male signals is still not well understood. Here, we tested how female and male forays are associated with short-range visual and long-range acoustic signals (dawn song). We used an automated radio-tracking system to follow the movements of wild great tits (Parus major) to other territories in relation to male dawn song, plumage ornaments, and extra-pair paternity. We show that both sexes frequently forayed into others’ territories throughout the breeding period. Movements of both males and females were associated with male song, but not with plumage ornaments. Contrary to our expectations, females stayed away from territories where males sang elaborately, while males were attracted to those territories. Moreover, neither female nor male forays were associated with the occurrence of extra-pair offspring. Our results thus suggest that while forays into other territories are associated with male dawn song, females may not be attracted and males not repelled by dawn song. This sheds a different light on the sex-specific effects of male advertisement signals, expanding the view on the selection pressures shaping such communication systems.

Methods

We used the automated radio-tracking system called “Encounternet” (Encounternet LLC, Portland, USA) to track movements of male and female great tits (Parus major) during the breeding season. We placed Encounternet-receivers up to 5 m from nest boxes at a height of approximately 2 m to monitor tagged birds entering the area around a nest box. From the raw logs saved by each receiver, we exlcuded logs estimated to be further away than 15m and calculated visits using a sliding window approach, treating a bird as present in the area as long as its tag was logged by the respective receiver at least three times during any 30 second time window (i.e. the receiver logged 50% of the signals sent out by the tag in 30 seconds). This way, we considered any time a bird was present near a nest box that was not its own breeding box as an extra-territorial foray/visit to that nest box area. For details on the tracking method and data processing see the mansucript method section and supplementray material. We additionally quantified male vocal (dawn singing) and plumage (yellowness and size of the black breast stripe) ornaments and determined the occurence of extra-pair offspring in broods (details on methods provided in manuscript). Please see the read_me txt file for detailed descriptions of all variables inlcuded in the provided data files. 

Usage Notes

Please see the read_me txt file for detailed descriptions of all variables inlcuded in the provided data files. 

Funding

Dutch Research Council (NWO), Award: 824.15.012

Dutch Research Council (NWO), Award: 824.15.012