Acoustic signals play a key role in shaping the relationships in birds. Common cuckoos Cuculus canorus are known to produce various call types, but the function of these calls has only been studied recently. Here, we used a combination of field recordings (conducted in 2017) and playback experiments (conducted in 2018) to investigate the functional significance of common cuckoo calls. We found significant differences in the characteristics between male two‐element “cu‐coo” and three‐element “cu‐cu‐coo” calls, with these two call types being used in different contexts. The three‐element male “cu‐cu‐coo” calls were associated with females emitting their “bubbling” call. Playback experiments revealed that both males and females exhibit stronger responses to playing female “bubbling” calls than with the calls of the Eurasian sparrowhawk (Accipter nisus) serving as a control, suggesting a significant intraspecific communication function for this call type. However, we did not find any evidence to support mate attraction in male calls, as females were not stimulated by playback of male calls compared with sparrowhawk calls in the control group.

Investigations on bird vocalizations have largely focused on males. Female vocalizations are widespread in birds but few studies have investigated female vocal characteristics, particularly in non-Passeriformes. In this study, we use new field recordings from China, and calls available from an online sound library to examine temporal patterns, call consistency and geographical variation in vocalizations of female common cuckoos Cuculus canorous. The peak in vocal activity (both male and female) was in the morning, which contrasts to what would be predicted if the sole function of the female call was to distract the attention of hosts after parasitizing a host's nest in the afternoon. Both male and female common cuckoos were more vocally active in sunny weather, than rainy weather. We also found larger intra-individual variation in female rather than in male calls, which may benefit female cuckoos by increasing stimulation to host species. Peak frequency of female calls decreased with increased latitude, while differences in female call features were not associated with geographic distance. In summary, our findings that female calls are used in the morning, rather than at peak egg laying, yet are highly variable and show little geographic patterns suggest that the function of these female calls may be more variable and intricate than previously thought. However, because research on female vocalizations is underrepresented, future studies are still needed.

26Numerous studies have identified individually distinctive vocal characteristics and call consistency in 27 different bird species. If these are to be utilised as non-invasive markers for monitoring purposes, then 28 these vocal characteristics must remain stable over time. Three recent studies have shown that it is 29 possible to identify individual male Common Cuckoo (Cuculus canorus) based on vocal characteristics 30 but whether these are stable over the duration of a breeding season, remains unknown. We recorded 31 1032 syllables from 30 male Common Cuckoos in a Northeast Asian population. We colour-banded six 32 of these males and made repeated recordings of their cu-coo advertisement call across a 19-day period 33 of the breeding season in China. We used three methods to identify individuals: discriminant function 34 analyses (DFA), correlation analysis (CA) and spectrographic cross-correlation (SPCC). We also used 35 repeatability analysis to test whether call consistency (the number of syllables in each calling bout) was 36 repeatable within individuals. Based on the same day recordings, calls from the same male were more 37 similar in their characteristics than those of different males, and yielded correct rates of classifying 38 individuals of 93.6% (SPCC), 90.8 % (DFA), and 71.5% (CA). However, these rates declined to 40.5% 39(SPCC), 40.7% (DFA) and 27% (CA) when using recordings over the 19-day period. Call consistency 40 was repeatable within individuals across two successive calling bouts, but this individual repeatability 41 disappeared when several (more than two) calling bouts from the same day or bouts from the different 42 days were included in the analyses. Declines in the correct rate of identifying individual male cuckoos 43 and call consistency in this study raises concerns that individual male cuckoo calls may be more 44 variable than previously thought. 45 4

No abstract

Reproduction is believed to contribute to the frequently observed seasonal cycles in parasite loads in many organisms, as an investment in reproduction by the host could result in a higher susceptibility to parasites. In this study, we examined the impact of breeding season on haemosporidian infection in free-range chickens (Gallus gallus domesticus). We sampled a total of 122 chickens (66 chickens during the breeding season of April 2017 and 56 chickens during the non-breeding season of January 2017) to test for haemosporidian infections. The result showed that 56 out of 66 chickens examined during the breeding season tested positive for parasites (84.8% parasite prevalence), whereas 39 out of 56 chickens tested positive for parasites during the non-breeding season (69.6% parasite prevalence). Moreover, among the 11 Leucocytozoon lineages and 2 Plasmodium lineages identified, the parasite lineages that infected chickens during the breeding season were more diversified than those that affected chickens during the non-breeding season. This study indicated that chickens have a higher incidence of haemosporidian infection and a greater diversity of haemosporidian parasite lineages during the breeding season relative to the non-breeding season.