Heronry distribution and site preference dynamics of tree-nesting colonial waterbirds in Tamil Nadu

Anthropogenic disturbance and climate change have significantly affected the distribution of wetlands globally and particularly in Asian countries. Various types of wetlands are harboured across all the biogeographic zones in India. These wetlands provide vital ecological services and are rich in biodiversity. However, anthropogenic pressures continue to be a threat to these wetlands by affecting the flora and fauna that depend on them. Tree-nesting colonial waterbirds are vulnerable to these pressures as their colonies are typically located in wetlands and associated areas. Disturbances to these areas have resulted in the loss or shifting of many heronries. The present study was conducted in the Indian state of Tamil Nadu during the period of 2017–2019 to document the existing and previously unknown heronries of the landscape. A total of 101 heronries were documented in 22 districts. The Little Cormorant was the most dominant species, occurring in 79% of the sites, with relative abundances of 24% and 26% during 2017–2018 and 2018–2019, respectively. A total of 23 tree species were utilized by the birds for nesting and Vachellia nilotica trees were used for nesting in about 25% of the heronries. 19% of the heronries were situated inside protected areas and 81% were located outside protected areas. Out of the 58 active nesting sites reported in 2005, 43 have been lost or are no longer active. Species distribution modelling with presence only data indicated that the sites with a high probability of occurrence were confined to the major waterbodies and rivers. Spatial correlation showed that the heronries were dispersed randomly across the landscape. The population dynamics within heronries and colonial nesting waterbirds’ response to various environmental factors must be monitored continuously to conserve these heronries.

Gulls of a feather do not sleep whenever—circadian rhythm of activity of black-headed gulls Chroicocephalus ridibundus during the incubation period

Many vertebrates exhibit a diel activity, steered by light–dark cycle. However, some colonial waterbirds, in that several species of gulls, are active not only in day hours but also at night. In this study, we aimed to investigate 24 h cycle of black-headed gulls (BHG) Chroicocephalus ridibundus activity with focus on sleep behaviour. We expected that 24 h patterns of activity differ between colonies located in various habitats, and within a colony between nests located in the centre vs at the edge. We studied behaviour based on 9600 of 30 s videos from camera-traps taken in six colonies and data from 10 GPS-tracked individuals from one colony recorded during incubation. BHGs stayed active on average during 48.1% of a night, mainly spent on passive and active nest defence, and on nest maintenance. BHGs spent similar time on these activities in day hours. Individuals breeding in the colony centre slept at night longer than those at its edge. BHGs stayed active during on average 76.5% of daytime. In two urban colonies with the highest nest densities and highest level of light pollution birds slept less during the day than in other studied colonies (three rural and one urban) characterized by lower densities and light intensity after sunset near the colony. Knowledge of nocturnal behaviour is crucial to comprehend 24 h activity patterns of an organism, especially to understand flexibility of behaviour crucial for restoration, like sleep.

Double-Crested Cormorant Disturbance: Restoration Potential for a Forested Urban Park

This paper examines the relationship between double-crested cormorant nesting activity and urban deforestation in Toronto’s Tommy Thompson Park (TTP). TTP is located on a human constructed spit, providing habitat for colonial waterbirds to nest along Lake Ontario’s shoreline. In recent decades, double-crested cormorant colonization has resulted in the deforestation of the western edge of the park. This deforestation is causing a steady retreat of tree cover, where newly exposed soils are vulnerable to colonization by invasive plants and erosive wind and wave action. Following a 30x30 m systematic sampling approach, geospatial interpolation of point data describing current soil physical and chemical properties is used to create continuous soil prediction surfaces. Interpolated surfaces are then combined to create site suitability maps using multicriteria evaluation (MCE) to weight the soil variables, and to provide a ranked output of desirable site locations for species-specific re-vegetation potential. Keywords: double-crested cormorant, urban forestry, restoration, kriging, multi-criteria evaluation

Double-Crested Cormorant Disturbance: Restoration Potential for a Forested Urban Park

This paper examines the relationship between double-crested cormorant nesting activity and urban deforestation in Toronto’s Tommy Thompson Park (TTP). TTP is located on a human constructed spit, providing habitat for colonial waterbirds to nest along Lake Ontario’s shoreline. In recent decades, double-crested cormorant colonization has resulted in the deforestation of the western edge of the park. This deforestation is causing a steady retreat of tree cover, where newly exposed soils are vulnerable to colonization by invasive plants and erosive wind and wave action. Following a 30x30 m systematic sampling approach, geospatial interpolation of point data describing current soil physical and chemical properties is used to create continuous soil prediction surfaces. Interpolated surfaces are then combined to create site suitability maps using multicriteria evaluation (MCE) to weight the soil variables, and to provide a ranked output of desirable site locations for species-specific re-vegetation potential. Keywords: double-crested cormorant, urban forestry, restoration, kriging, multi-criteria evaluation

Nesting tree selection by scattered heronry birds of drought prone Northern Bankura, West Bengal, India: preference of Phoenix sylvestris near wetland-associated habitats

The present study was conducted in the Gangajalghati block of Northern Bankura, India, to investigate the habitat and nest tree preference of three colonial waterbirds viz. Nycticorax nycticorax, Egretta garzetta, and Ardeola grayii. The study sites were surveyed for 20 months between 2017 and 2020. A total of 817 nests with an average of 204 per year were recorded on 13 tree species. Nycticorax nycticorax showed the maximum nest count followed by Egretta garzetta and Ardeola grayii. Relative abundance data revealed Phoenix sylvestris as the most abundant species (45%) of the area and harbours the highest proportion (33%) of nests. Pooled nest count data showed significantly higher (p < 0.01) total nest counts in the wetland associated habitats than others. The study observed more nest density of all three species near a cluster of small ponds than in a large water body. Year-wise difference in cumulative nest number and mean nest abundance of all three species was statistically insignificant. The interspecific nearest neighbour on Phoenix sylvestris were Egretta garzetta (88.37%) for Nycticorax nycticorax and Nycticorax nycticorax (83.25%) for Egretta garzetta and Ardeola grayii. Further, the study evaluated the impact of two tropical cyclones (Amphan and Fani) on the total nest count and found that more than 75% nests (p < 0.05) were destroyed by the mighty Amphan in May 2020. The study provides a baseline data on nesting trees and habitat preference of three species of heronry birds from Northern Bankura.

Artificial Wetlands as Breeding Habitats for Colonial Waterbirds within Central Romania

The historical loss of natural wetlands in Romania is significant. The building of lakes, ponds, and dams has compensated for some of these losses, as was the case in the study area, the artificial wetlands designated as the Natura 2000 (special protection area, SPA) and Ramsar sites. In this context, to evaluate the conservation status of colonial waterbirds (cormorants, herons, and egrets), we analyzed actual distributions, habitat selection, features, and population sizes. Standardized counting of colonial species was used, supplemented by nest counting and colony-area estimation during winter, and drone footage. All species and their colonies were built in artificial or anthropically influenced habitats. Concerning distribution and population sizes, Phalacrocorax carbo and Microcarbo pygmeus were found to nest only in central Romania. The pair numbers of Ardea alba, Ardea purpurea, Ardea cinerea, and Nycticorax nycticorax in the area exceeded 1% of the national minimum breeding population. There was a statistically significant positive trend of breeding populations for Ardea alba, Nycticorax nycticorax, and Egretta garzetta. In conclusion, these artificial wetlands offer optimal breeding conditions for a relatively large diversity of colonial bird species over areas that are not very large.