Drone assessment of habitat selection and breeding success of Gull-billed Tern <em>Gelochelidon nilotica</em> nesting on low-accessibility sites: a case study

Abstract

The use of drones in the study of waterbird breeding biology has received considerable attention in the last years, but very few studies were made along the Mediterranean. We studied habitat selection and breeding success of the Gull-billed Tern Gelochelidon nilotica in two colonies inside fish farms along the Italian Adriatic coastline, using a small, commercial drone. Both colonies were located on small islets surrounded by very shallow water and clayey bottoms, thus being difficult to access. Compared with availability, the Gull-billed Terns selected quadrats higher above the water level, with a higher vegetation cover, which lay farther from the water edge, contain less water, and which are more frequently located in the center of the islands. 147 of 178 clutches (mean clutch size ± SD: 2.61 ± 0.58) hatched 383 chicks (82.5%; 2.15 ± 1.09 chicks per nest), with large differences between the two colonies. Hatching success was 95.0% and 69.1%; the most common cause of egg loss was flooding (97.0%). Nest attendance could easily be ascertained by 30-m above ground level drone-derived imagery. The use of a drone allowed the study of some aspects of the breeding biology of the Gull Billed Tern in two breeding sites where the traditional field approach, i.e. researchers reaching the sites by boat, would have been very difficult, causing unavoidable and prolonged disturbance to the nesting adults.

Delay in Adélie penguin nest occupation restricts parental investment in nest construction and reduces reproductive output

“…We propose that larger nests offer an advantage against undesirable weather conditions including moisture after snow melt by raising the nest bowl away from the ground (Ainley et al., 1983 ; Fargallo et al., 2001 ; Moczydłowski, 1989 ; Stokes & Boersma, 1998 ). Although nest flooding occurs across a range of ecosystems (Scarton & Valle, 2020 ; Windhoffer et al., 2017 ), for polar species, the occurrence of precipitation in the form of rain is uncommon (Robinson et al., 2020 ) outside of the Western Antarctic peninsula (Chapman et al., 2011 ; Thompson et al., 1994 ; Turner et al., 2005 ), but can occur from water run‐off after snow melt. Historically, precipitation is thought to be responsible for major seabird population changes at other sites in Antarctica (Gao et al., 2018 ) and is known to affect the breeding success and phenology of Adélie penguins (Boersma, 2008 ; Hinke et al., 2012 ).…”

Plastic Debris in Nests of Two Water Bird Species Breeding on Inland Saline Lakes in a Mediterranean Biosphere Reserve

“…In our study area, agricultural intensification could be related to a decrease in suitable feeding habitats for this species [ 43 ] because it hunts insects in land areas near the wetlands to feed chicks [ 38 ]. These colonial breeders build their nests on the ground on islets with clayey bottoms and high vegetation cover that are surrounded by shallow water [ 44 , 45 ] and use sticks, algae, stones, and other debris as material ( Figure 1 D).…”

Are we overlooking Natura 2000 sites? Lessons learned from a transnational project in the Adriatic Sea

“…Occasionally, the management authority also monitors the spatial distribution of species, density, coverage, species richness, and community structure (Markov and ECOSS Partnership, 2019). Data on the status and distribution of P. marinus, A. fallax, and seagrasses are deficient, while much more information is available for the identified target seabirds (Ente Regionale Parco Delta del Po Veneto, 2010; Verza et al, 2011;Bon et al, 2013;Scarton et al, 2013;Verza, 2015;Scarton et al, 2018;Valle and Scarton, 2018;Miocǐc-Stosǐcé t al., 2020;Scarton and Valle, 2020;Valle and Verza, 2020;Scarton, 2022). However, regular monitoring, necessary to detect population trends of these species and guide the adoption of adequate measure, is still lacking (Markov and ECOSS Partnership, 2019;Golec and ECOSS Partnership, 2020).…”