Birds

Noteworthy

We completed the Amaala islands bird baseline assessment. Compared to TRS, the number of islands and total area available for birds is much smaller (only three islands at Amaala). However, a total of 2,129 nests of seven species were counted.

At TRS, we completed the second year of island bird populations monitoring, counting more than 25,000 nests of 11 species. Breeding population sizes were similar to those counted in 2021.

We extended previous surveys of breeding success, assessing seven species in 2022 and detecting a large variability among them.

The vulnerable Sooty falcon remains a priority species for us. Forty-eight breeding pairs were counted at TRS in 2022, an increase from the 41 pairs counted in 2021. We also counted 17 pairs of this species at Amaala - all on An Numan Island, making it an important breeding location for this vulnerable species.

We initiated a telemetry study by tagging 30 Sooty falcons (both adults and juveniles) in 2021. This allows us to follow their movements and understand which habitats they use in our area during the breeding season as well as where they migrate to over-winter. This will also help us monitor juvenile survival and assess if they will return to our area to breed.

Methods

The survey area at Amaala consists of the three islands suitable for birds. We also visited 92 islands at TRS that were surveyed as part of our TRS baseline in 2021 and will be part of our ongoing monitoring program.

The high-priority Amaala bird species for which abundance and distribution were assessed are: Sooty falcon (Falco concolor), Osprey (Pandion haliaetus), Lesser crested tern (Thalasseus bengalensis bengalensis), Great crested tern (Thalasseus bergii velox), White-cheeked tern (Sterna repressa), Bridled tern (Onychoprion anaethetus), Sooty gull (Ichthyaetus hemprichii), White-eyed gull (Ichthyaetus leucophthalmus), Crab plover (Dromas ardeola) and Caspian tern (Hydroprogne caspia). These species were chosen based on:

1. Their global and local conservation and classification in IUCN Red list (Symes et al., 2017)

2. Their identification as high-conservation priority species for Saudi Arabia (Abuzinada et al., 2003; Boland & Burwell, 2020)

3. Other local considerations, including whether species are endemic to the region.

At Amaala the breeding success was assessed for Ospreys but not for Sooty falcons, since Sooty falcon nests at Amaala are too inaccessible and chicks cannot be seen. However, at TRS breeding success was assessed for seven species (including the Sooty falcon).

The study species were divided per season based on their breeding time:

4. Winter breeders: Osprey, Caspian tern and Red-billed tropicbird.

5. Summer breeders: White-cheeked, Lesser crested, Great crested and Bridled terns; Crab plover; White-eyed and Sooty gulls.

6. Autumn breeders: Sooty falcon.

At TRS we surveyed the Summer and Autumn breeders and the Red-billed tropicbird as part of our ongoing monitoring program.

Bird populations are counted at the peaks of the breeding season - at late egg stage/early chick-rearing. If colonies are counted too early, the late breeders are missed; if counted too late, the early failures are missed. The peak is calculated as a certain number of days after the first egg is spotted in a colony. This number differs among species depending on their synchronicity in egg laying. Species were aggregated in different categories (terns, gulls, plovers and falcons) and the first species laying eggs was taken as reference to start the counting.

For TRS re-surveys, we assessed 11 species surveyed there for the 2021 baseline with the same methods.

Colony & Nest Surveys

At Amaala the islands of An Numan, An Nabqiyah and Awandia were extensively walked in February, May, July and September to assess abundance and distribution of the breeding birds listed above. During the first visit, the osprey nests were located. Once a nest was found, it was categorized as either: i) “old nest,” if it was no longer used by individuals, ii) “active nest,” if any signs of activity were found (fish scrap, droppings, new nesting material); or iii) “nest with breeding pair,” if it was actively used by a breeding pair and contained either eggs or chicks. During the second and third visits, summer-breeding birds’ numbers were assessed and the areas of the colonies geo-referenced. In May, observations of Sooty falcons were also recorded. Finally, during the fourth visit, An Numan Island was surveyed to locate and geo-reference Sooty falcon nests.

At TRS, islands were surveyed from June to October to detect Summer and Autumn breeders as per 2021.

Breeding Success

To assess the breeding success at TRS, at least 30 nests for the seven selected species were visited a minimum of two times each to assess how many chicks fledged out of the eggs laid. The species selected were Red-billed tropicbird; Osprey (in Amaala); Brown booby; Great crested, Lesser crested and White-cheeked terns; and Sooty falcon. Different techniques were used such as visual surveys, camera traps deployment and photogrammetry. We’re still refining our methods for these types of surveys, but we intend to maintain and expand them in coming years.

Results

Osprey Census & Breeding Success

The Osprey is the only member of the Pandionidae family and among the world’s most-studied birds of prey. It is the only raptor that plunge-dives to catch live fish as its main prey source. Ospreys occur on all continents excluding Antarctica, and they live at the shores of shallow waters, from coastal salt marshes to reservoirs and inland lakes. During the breeding season, they need trees or predator-free islands where they can build their large nests made of sticks. At TRS and Amaala sites, they nest on islands, building nests on the ground that can reach 2m in height. The different breeding periods (phenology) are indicated in the table below. One island rarely hosts more than one breeding pair, unless it’s big enough.

Ospreys were recorded frequenting An Numan Island at Amaala during previous surveys, but before this year, the location of the nests and population size had not been assessed.

Table:

Species Month (divided in fortnights)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Osprey

Out of 13 osprey nests on An Numan, only two were occupied by breeding pairs. The two pairs had three and four eggs, respectively. During the second visit, the breeding success was assessed and both pairs successfully fledged all their chicks.

Also, nine nests were found on Nabqiyah, one of which was occupied by a breeding pair. A total of six ospreys were counted on the islands - presumably two parents with four fledged chicks (to be confirmed during the next breeding season). Only two nests were found on Awandia, one of which was occupied by a breeding pair. Four ospreys were counted on the island: the two parents plus two fledged chicks.