Connectivity dynamics in Irish mudflats between microorganisms including Vibrio spp., common cockles Cerastoderma edule, and shorebirds

Shellfish, including the key species the common cockle Cerastoderma edule, living and feeding in waters contaminated by infectious agents can accumulate them within their tissues. It is unknown if microbial pathogens and microparasites can subsequently be transmitted via concomitant predation to their consumers, including shorebirds. The objective of this study was to assess if pathogens associated with C. edule could be detected seasonally in the faeces of shorebirds that feed on C. edule and in the physical environment (sediment) in which C. edule reside, along the Irish and Celtic Seas. Two potentially pathogenic global groups, Vibrio and Haplosporidia, were detected in C. edule. Although Haplosporidia were not detected in the bird faeces nor in the sediment, identical strains of Vibrio splendidus were detected in C. edule and bird faecal samples at sites where the oystercatcher Haematopus ostralegus and other waders were observed to be feeding on cockles. Vibrio spp. prevalence was seasonal and increased in C. edule and bird faecal samples during the warmer months, possibly due to higher seawater temperatures that promote the replication of this bacteria. The sediment samples showed an overall higher prevalence of Vibrio spp. than the bird faecal and C. edule samples, and its detection remained consistently high through the sites and throughout the seasons, which further supports the role of the sediment as a Vibrio reservoir. Our findings shed light on the fact that not all pathogen groups are transmitted from prey to predator via feeding but bacteria such as V. splendidus can be. As most of the wading birds observed in this study are migratory, the results also indicate the potential for this bacterium to be dispersed over greater geographic distances, which will have consequences for areas where it may be introduced.

Paternal effects in the initiation of migratory behaviour in birds

What determines why some birds migrate and others do not? This question is fundamental to understanding how migratory systems are responding to environmental changes, but the causes of individual migratory behaviours have proven difficult to isolate. We show that, in a partially migratory population of Eurasian oystercatchers (Haematopus ostralegus), the migratory behaviour of progeny follows paternal but not maternal behaviour, and is unrelated to timing of hatching or fledging. These findings highlight the key role of social interactions in shaping the migratory behaviour of new generations, and thus the spatio-temporal distribution of migratory populations.

[First nesting of the Eurasian Oystercatcher Haematopus ostralegus in the inland Po Valley (Italy)]

[Here we present the first report of Eurasian Oystercatcher nesting in the Province of Mantua; the nest was found on a sandbank on the Po river, in June 2017. This is the first case reported for the Po Valley away from the Adriatic coast]. [Article in Italian]