Begging call mimicry and formation of host-specific lineages in the shining bronze-cuckoo Chalcites lucidus

Collection methods We recorded begging calls of the three shining bronze-cuckoo subspecies and their respective hosts from Australia, New Caledonia and New Zealand in the period July – January, which corresponds with the breeding season of hosts and cuckoos in the Australasian region. We regularly monitored active nests at our field sites at 2-days intervals, therefore we recorded laying, hatching and fledging dates with a precision of 2 days. As we assessed the timing as the average between two nest checks, this resulted in an uncertainty of ±1 day. We recorded begging calls in the period 2005-2009 in an open eucalypt woodland in Australia (Campbell Park, 35°16′S, 149°10′E), in the period 2005-2007 in areas of forests and scrubs in New Zealand (Tawharanui Regional Park, North Island: 36°22′S, 174°50′E) and in the period 2015-2023 at three sites on the main island (Grande Terre) of New Caledonia in areas of rainforest (Parc Provincial des Grandes Fougères, 21°39′S, 165°46′E), open forest and thickets (Farino and surrounding, 21°40′S, 165°46′E) and open dry forest and savannah (Domaine de Deva, 21°36′S, 165°24′E). Field methods for the monitoring of host nests and cuckoo breeding are described elsewhere (Anderson et al., 2013; Attisano et al., 2019; Medina & Langmore, 2019). We collected a total of 23 recordings from 14 cuckoo nestlings aged between 3 and 14 days: 10 recordings from 8 Chalcites lucidus plagosus from Australia and 13 recordings from 6 C. l. layardii from New Caledonia. We could not record young cuckoo nestlings C. l. lucidus in New Zealand, but we included 4 recordings from one cuckoo nestling 19 days-day-old and three 20 days-day-old cuckoo fledglings (recorded on the fledgling day). Shining bronze-cuckoo young fledge around 20 days after hatching and remain close to the nest for at least 1-2 days while being fed by host parents. We collected a total of 32 recordings of host nestlings from 23 nests, with each nest containing from 1 to 3 host nestlings: 8 recordings from 7 nests of yellow-rumped thornbills from Australia containing chicks 3 to 12 days old, 18 recordings from 11 nests of fan-tailed gerygone from New Caledonia containing chicks 3 to 11 days old and 6 recordings from 6 nests of grey warbler from New Zealand containing chicks 8 to 12 days old. In Australia, we recorded begging calls for 20 minutes using a Sony tie-clip miniature microphone (ECM T6) and a digital recorder (TASCAM DR-05). The microphone was clipped to vegetation approximately 20 cm from the nest entrance. In New Caledonia, we recorded nestlings with a digital recorder (Tascam DR-40) and a condenser microphone (Shure SM93), placed at the bottom of the nest at a distance of 1-3 cm from the internal incubation chamber at multiple feeding events during 2-3 hours long recording sessions. In New Zealand, we recorded nestling begging calls with a Sennheiser ME 66 microphone or a Panasonic RP-VC201 stereo tie-clip microphone, depending on nest accessibility, onto a Sony MZ-NH700 Hi-MD Minidisc. Young cuckoo fledglings were opportunistically recorded with the Sennheiser ME66 directional microphone, while being fed by their host parents outside the nest. Data structure The main dataset Begging_data is presented in a CSV format and includes: RecordingID: name of the audio file Species: latin name of the recorded species SpeciesID: categorical variables identifying the species IndividualID: sequential number for the individual nestling recorded Type: categorical variables identifying host vs parasite Site: categorical variable indicating the area where the recording was collected Age: age of the nestling when recording was collected ThreeAgeGroup: categorical variable to subset data according to nestling age Call: numerical variable identifiyng the call number for each individual nestling CallRate: average number of calls per second for each nestling Duration: duration in s of the call LowFreq: lower frequency in Hz of the call HighFreq: higher frquenzy in Hz of the call FreqBandwidth: frequency bandwidth (HighFreq-LowFreq) in Hz of the call Freq5: frequency in Hz at which the total energy of the call exceeds 5% Freq95: frequency in Hz at which the total energy of the call exceeds 95% CenterFreq: frequency in Hz dividing the call in two intervals of equal energy PeakFreq: frequency in Hz at which the highest amplitude occurs AvgEntropy: variation of sound intensity across time and frequency in bits The file BeggingAnalysis.Rmd includes the R code in RMarkdown format with the full analysis of the data as described in Attisano et al., 2025 https://doi.org/10.1016/j.anbehav.2025.123083