Environmental characteristics of shallow bottoms used by Greater Flamingo Phoenicopterus roseus in a northern Adriatic lagoon

Abstract

Since the beginning of this century, Greater FlamingoPhoenicopterus roseusflocks have been observed regularly when feeding in the large extensions of shallow bottoms in the Lagoon of Venice (NE Italy), the largest lagoon along the Mediterranean. Nowadays thousands of flamingos are present throughout the year. Between 2013 and 2017 I collected data on the environmental features of the shallow bottoms used by feeding flocks, along with measurements of flight initiation distance (FID) of Greater Flamingo in response to the approach of boats and pedestrians. Shallow bottoms were shown to be used when covered with approximately 10 to 60 cm of water. All the feeding sites were in open landscapes, with low occurrence of saltmarshes in a radius of 500 m. The bottoms were barely covered with seagrasses (<4% of the surface around the survey points) and were mostly silty. Feeding flocks were on average 1.2 km far from the nearest road or dyke, while the mean distance from channels that could be used by boats was about 420 m. The mean FID caused by boats or pedestrians was 241 m ± 117 m (N = 31, ± 1 SD) without significant differences between those for the two disturbance sources. The use of shallow bottoms by the Greater Flamingo appears governed primarily by the tidal cycle, but boat disturbance probably modifies this effect. According to FID values, a set-back distance of 465 m is suggested to reduce the disturbance caused by boats and pedestrians to the flamingo feeding flocks.

Rapid drone semi‐automated counts of wintering Greater Flamingos (Phoenicopterus roseus) as a tool for amateur researchers

“…In the present study, drone counts conducted at elevations exceeding agitation distances did not elicit any detectable disturbance to birds. The lack of any detectable disturbance by drones flying at 70 m agl, as found in the present study, is particularly important, as this species is known for its extremely high sensitivity to both human and boat disturbance in other areas (Johnson & Cezilly 2007), including the neighbouring Lagoon of Venice (Scarton 2017). Unfortunately, the current study was not designed to test disturbance.…”

“…2017 for a review, but see Valle & Scarton 2019b). Many human activities can negatively affect flamingos, including recreation (Yosef 2000), clam harvesting (Scarton 2017), birdwatching (Galicia & Baldassarre 1997) and research activities (Johnson & Cezilly 2007). In the present study, drone counts conducted at elevations exceeding agitation distances did not elicit any detectable disturbance to birds.…”

“…2005). Large flocks are often found in the fish farms surrounding the lagoons, where the birds feed and rest (Scarton 2017).…”

“…obs.). In the remaining two cases (for three flocks overall; two flocks were surveyed from the same vantage point), a set‐back distance (the mean flight initiation distance plus two standard deviations) of 500 m (as suggested for the heavily disturbed population wintering in the neighbouring Lagoon of Venice; Scarton 2017) was respected to lessen the impact of disturbance. Mean distance between observer and Flamingo flock was 319 ± 126 m (mean ± sd) according to measurement by drone remote control.…”

“…A Greater Flamingo population of approximately 10 000 birds regularly winters in this study area (Bon et al 2005). Large flocks are often found in the fish farms surrounding the lagoons, where the birds feed and rest (Scarton 2017).…”