Population Trend of Colonially Nesting Heron Species in Greece.

Simple Summary: We studied the nesting population trends of the colonially nesting heron species in Greece from 1988 to 2018, aiming to identify drivers of these trends and thus inform colony/wetland conservation measures. Two species (Cattle Egret and Squacco Heron) had a positive trend, while three species (Black-crowned Night Heron, Little Egret and Grey Heron) had a negative trend. The Purple Heron presented a stable trend. Our results suggest that: (a) The Natura 2000 network and the operation of the protected areas Management Authorities have positively affected heron species nesting population trend or range expansion, (b) national wetland restoration efforts have facilitated the expansion of most heron species' breeding range via the establishment of new colonies, and (c) colonies located outside protected areas were—especially in the case of the Grey Heron—most likely to have a declining nesting population trend. The drivers behind the observed population trends differed among species, even among those sharing the same breeding sites. This suggests that the nesting population trends could be due to ecological changes at both the breeding and at the wintering sites. Our results emphasize the importance of continuing wetland restoration efforts, developing heron-friendly farming practices, and adopting a systematic nationwide survey of colonies. Heron colonies are dynamic components of wetlands. Therefore, their systematic monitoring is important for the management of both birds and wetlands. During the period 1988–2018, we counted breeding pairs of seven colonial breeding heron species at 65 colonies across 37 wetlands in Greece. We considered as annual variables of a population: (a) years since 1988, (b) Natura 2000 network inclusion, (c) protected area management authority overseeing, (d) wetland type (new or restored), and (e) new colonies (established after 2003). The Cattle Egret Bubulcus ibis and the Squacco Heron Ardeola ralloides had a positive breeding population trend. The Black-crowned Night Heron Nycticorax nycticorax, Little Egret Egretta garzetta, and Grey Heron Ardea cinerea had a negative trend, while the Purple Heron Ardea purpurea population was stable. The Great White Egret Ardea alba bred sporadically at only a few sites which precluded the evaluation of its population trend. The informative population variables differed among species, even of those at the same colony, which suggests trends are also affected by conditions at wintering grounds. The study highlights the need for the systematic monitoring of heron colonies and the protection of foraging/breeding areas in order to reverse the observed negative population trends. [ABSTRACT FROM AUTHOR]

Copyright of Birds (2673-6004) is the property of MDPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)