Crab Plover Dromas Ardeola Research Articles

From the Arabian Peninsula to Indian shores: Crab Plover Dromas ardeola Paykull, 1805 (Aves: Charadriiformes: Dromadidae) breeding at Point Calimere, India

Crab Plover Dromas ardeola is endemic to the subtropical and tropical coastlines of the Indian Ocean. It breeds along the easterncoasts of Africa, the Persian Gulf, and southern coasts of the Arabian Peninsula; occurs also in the western Madagascar and most islands northwards to Seychelles. It is a winter visitor to Pakistan, Gujarat, and peninsular India, Andaman & Nicobar Islands, Lakshadweep, northern Sri Lanka, Maldives, and a vagrant to Bangladesh. The objective of this study was to assess the breeding records of the Crab Plover in Point Calimere. After some preliminary surveys and interactions with local birders, between June and August 2023, boat surveys and foot surveys were carried out in the Great Vedaryanam Swamp (GVS) and nearby islets to document the presence of Crab Plover and locate its nests. The presence of five nests of D. ardeola was recorded in Manaaran Theevu islet near Siruthalaikkadu of GVS. This observation marks the first documentation of breeding of Crab Plover in the Indian subcontinent. In the context of species conservation within the peninsular Indian region, there is a need for comprehensive and continuous monitoring of breeding sites.

Demography of a stable population of Crab Plovers wintering in Oman

The monotypic Crab Plover Dromas ardeola winters around the shores of the Indian Ocean and breeds in colonies on islands around the Arabian Peninsula. The IUCN lists the world population of Crab Plovers as stable, but long-term survey data or demographic estimates regarding the species status are lacking. Here, we use survey and demographic data collected from 2011 to 2015 to study the status of the population of Crab Plover at their most important wintering area: the Barr Al Hikman Peninsula in the Sultanate of Oman. Our survey data showed that the population of Crab Plovers initially increased and then stabilized. The overall observed finite rate of population change ( $$\bar{\lambda }_{\text{obs}}$$ ) was estimated at 1.004 (0.995–1.013 95% Bayesian credible interval [BCI]), indicating a stable population (7000–9000 birds), that is possibly at carrying capacity. Based on mark-recapture data, the mean annual apparent survival probability of Crab Plovers was estimated to be 0.90 (0.85–0.94 95% BCI). We used counts of adults and yearlings to estimate the mean annual fecundity rate at 0.06 young per pair. Using these demographic values, the overall mean expected finite rate of population change ( $$\bar{\lambda }_{ \exp }$$ ) was estimated to be 0.949 (0.899–0.996 95% BCI), so there is a low chance that $$\bar{\lambda }_{\text{obs}}$$ and $$\bar{\lambda }_{ \exp }$$ overlap. $$\bar{\lambda }_{\text{obs}}$$ and $$\bar{\lambda }_{ \exp }$$ would completely match if about 450 Crab Plovers immigrate to Barr Al Hikman each year. Regional surveys show that yearling densities are higher closer to the breeding areas, so immigrants could be birds that during their first winter stayed close to their natal area. Our study support the IUCN listing of Crab Plover as stable, but further population-wide monitoring is required. From a conservation point of view it is important to continue monitoring because Crab Plovers breed and winter in a region that is rapidly developing.

Predatory risk favours intermittent incubation of a colonial burrowing shorebird, the Crab Plover Dromas ardeola

Intermittent incubation in birds is currently interpreted as the result of trade-offs between the needs of the embryo and those of the parents. However, the low nest attendance in some species is still puzzling. We studied the Crab Plover (Dromas ardeola), a tropical burrow nesting shorebird with very low incubation constancy (less than 55%) due to frequent recesses from incubation (on average 5 recesses/h), mostly spent in the colony area without any apparent function. We aimed to test whether such unusual incubation rhythm can be partly explained by the need to scan for approaching predators. Data collected at Dahret Island (Eritrea) between 2006 and 2014 support the antipredatory function of the incubation rhythm: (1) many recesses on the colony surface were so short (50% less than 37 s in the hotter periods) that a thermoregulatory function can be dismissed; (2) adults on the colony surface responded to approaching predators with alarm calls that drove most incubating Crab Plovers to run out of the burrows and to escape in flocks; (3) sound intensity sharply decreased inside burrows, which explains the delayed escape observed for 9% of the incubating birds; (4) the delayed exit when predators were still in the colony area rules out their permanence inside burrows as an alternative antipredatory strategy; (5) after the visit of a predator, adults restarted incubation with very short in-bouts (2 min on average) apparently in order to scan frequently for approaching predators. We discuss how burrow nesting, alarm calls, and the antipredatory reactions of adults (escape into or out of the burrows, flock flight, mobbing) and chicks (escape into burrows) might have favoured colonial breeding in Crab Plovers.

Little known chewing lice (Phthiraptera) infesting crab plover Dromas ardeola Paykull, 1805 (Charadriiformes: Dromadidae) from the Red Sea

Scanty information is available for many species of chewing lice of marine birds. Through this work we investigated one of most characteristic marine bird for chewing lice. Seven individuals of crab plovers Dromas ardeola Paykull, 1805 were trapped using standard mist nets on Humr Island in Farasan Archipelago, Saudi Arabia. Two species of chewing lice were found to infest these birds: Actornithophilus ardeolae Timmermann, 1954 of suborder Amblycera and Quadraceps brunneus (Nitzsch in Giebel, 1866) of suborder Ischnocera. Diagnostic characters, data of specimens examined, high definition photos and host distribution map are provided through this paper.

Food abundance explains the breeding season of a tropical shorebird, the Crab Plover Dromas ardeola

The timing of breeding in birds is a life-history trait that generally depends on food availability, but other factors may play a role, particularly in tropical areas where food availability is less seasonal than in temperate or polar areas. We studied the factors affecting the breeding season of the Crab Plover Dromas ardeola, a burrownesting colonial shorebird endemic to the north-western Indian Ocean. A reduced risk of burrow flooding, high temperatures suitable for exploiting solar incubation, a reduced interference by Palaearctic shorebirds during foraging, a reduced risk of predation by Palaearctic raptors and a high food abundance are all associated with the summer breeding season of the Crab Plover in our study area in Eritrea. In addition, we collected remotely recorded data associated with these advantageous environmental factors around breeding colonies in nine well-separated areas. Only average annual chlorophyll a concentration, a proxy of marine productivity, was significantly correlated with the start of the breeding season, which varies up to one month throughout the breeding range. We conclude that food abundance, with the likely high intraspecific competition due to coloniality, is strongly supported as the critical factor determining the nesting phenology of this tropical species.

Low incubation investment in the burrow‐nesting Crab Plover Dromas ardeola permits extended foraging on a tidal food resource

We used GPS data‐loggers, video‐recordings and dummy eggs to assess whether foraging needs may force the low incubation attentiveness (< 55%) of the Crab Plover Dromas ardeola, a crab‐eating wader of the Indian Ocean that nests colonially in burrows. The tidal cycle was the major determinant of the time budget and some foraging trips were more distant from the colony than previously known (up to 26 km away and lasting up to 45 h). The longest trips were mostly made by off‐duty parents, but on‐duty parents also frequently left the nest unattended while foraging for 1–7 h. However, the time spent at the colony area (47%) and the time spent roosting on the foraging grounds (16%) would have allowed almost continuous incubation, as in other species with shared incubation. Therefore, the low incubation attentiveness is not explained by the need for long foraging trips but is largely dependent on a high intermittent rhythm of incubation with many short recesses (5.8 ± 2.6 recesses/h) that were not spent foraging but just outside the burrow or thermoregulating at the seashore. As a result, the eggs were warmed on average only 1.7 °C above burrow temperature, slightly more during high tide periods and when burrow temperature was lower between 20:00 and 10:00 h, only partly counteracting the temperature fluctuations of the incubation chamber. These results suggest that low incubation attentiveness is due to the favourable thermal conditions provided by safe nesting burrows and by the hot tropical breeding season, a combination that allows simultaneous foraging by parents and the exploitation of distant foraging grounds. Why Crab Plovers engage in many short recesses from incubation still remains to be clarified but the need to thermoregulate at the seashore and to watch for predators may play a role.

English

The research was conducted in Ghabre Nakhoda, Nedelghar, Dara and Boneh islands in Khore Mosa Ramsar site in the Persian Gulf from May to December 2003 and 2012. Total count method was used to obtain the census of the nests and breeding population of waterbirds on the Islands. Thirty three (34) species of waterbirds were identified, of which eight species were breeders. The maximum breeding population of Lesser Crested Tern Sterna bengalensis, Swift Tern sterna bergii, Caspian Tern Sterna caspia, Bridled Terns sterna anaethetus, Western Reef Heron Egretta gularis and Crab Plover Dromas ardeola were 2551, 124, 120, 1310, 23 and 10500 pairs, respectively. Only two pairs of Little Egret Egretta garzetta had been bred in 2003 in the Ghabre Nakhoda. The islands have been identified as an "important bird area" (as a part of Shadeghan marsh) by Birdlife International proposed for protection as a part of the wildlife refuge of Shadeghan and suggested for to be classified as sensitive habitat for breeding seabirds. Key words: Breeding species, nest number, species diversity, Persian Gulf.

Feather mites of the genus Zachvatkinia Dubinin, 1949 (Astigmata: Analgoidea: Avenzoariidae) from Saudi Arabia: A new species and two new records.

Feather mites of the family Avenzoariidae (Acari: Astigmata: Analgoidea) are recorded for the first time in Saudi Arabia. A new avenzoariid species, Zachvatkinia (Zachvatkinia) repressae sp. n. (Avenzoariidae: Bonnetellinae), is described from the White-cheeked Tern, Sterna repressa Hartert, 1916 (Charadriiformes: Stemidae). The new species belongs to the sternae group and is closely related to Z (Z.) chlidoniae Mironov, 1989a. Two more species, Z. (Z.) dromae Mironov, 1992 and Z. (Z.) sternae (Canestrini & Fanzago, 1876), were collected from the Crab Plover Dromas ardeola Paykull, 1805 (Charadriiformes: Dromadidae) and the Sooty Gull Ichthyaetus hemprichii (Bruch, 1853) (Charadriiformes: Laridae), respectively. Among the 18 described species of Zachvatkinia Dubinin, 1949, including the new species, this is the fifth species recorded from a sternid host. The remaining 13 nominal species are associated with birds of the families Diomedeidae, Dromadidae, Hydrobatidae, Laridae, Pelecanoididae, Procellariidae and Stercorariidae. A checklist of world species of Zachvatkinia with data on their distribution and type hosts is also provided.

Birds Observation and Nest Count of Crab Plover <i>Dromas ardeola</i>, Western Reef Heron <i>Egretta gularis</i> and four Tern species on Ghaber Nakhoda Island (Persian Gulf) in 2003 and 2012

This research was conducted in Ghabre Nakhoda Island (30°20′26″ N 48°55′53″ E) in Khore mosa Creek from May 2003 to December 2003 and May 2012 to December 2012. The area of the island is about 3 hectare. The aim of this study is to provide a complete picture of the Present population of the colonial breeding waterbirds in Ghabre Nakhoda island in Khore Mosa Creek. Total count method was used to obtain the census of the nests and breeding population. Thirty tow species of waterbirds were identified in the island, of which eight species were breeder. Lesser Crested Tern Sterna bengalensis was dominant and indicates. The maximum breeder population of this species was 2500 pairs in 2003. Other breeder species were Crab Plover Dromas ardeola , Lesser Crested Tern Sterna bengalensis , Swift Tern Sterna bergii , Caspian Tern Sterna caspia , Bridled Terns Sterna anaethetus , Western Reef Heron Egretta gularis , and a small colony of White cheeked Tern Sterna repressa . The island has been identified as an Important Bird Area by Birdlife international proposed for protection as a part of the Shadeghan wildlife refuge and suggested for to be classified as sensitive habitat for breeding waterbirds. The main plant communities of the island are Atriplex sp, Stipa sp, Suaeda sp. and Halostachys sp..

Census and Phenology of Breeding Waterbirds on the Islands of Khan, Tahmadon, Om-Al-Gorm and Nakhiloo in the Persian Gulf, Iran

There are 4 islands Khan, Tahmadon, Om-Al-Gorm and Nakhiloo in the Mond Protected in Boshehr province in the Persian Gulf. This research was conducted in these islands from March 2008 to September 2012. Thirty four species of birds were identified in these Islands. Nine species were breeders. Bridled Tern Sterna anaethetus was dominant and indicates. The maximum population of this species was 29,461 pairs in 2006 in Nakhiloo. The Maximum breeding population of Lesser Crested Tern Sterna bengalensis was 11,783 pairs in 2012 in Nakhiloo, and Swift Tern Sterna bergii was estimated at 2,500 pairs in 2008. We estimated 92 pairs of Western Reef Heron Egretta gularis and 2,825 pairs of Crab Plover Dromas ardeola in 2005 in Om-Al-Gorm. The other breeders were Caspian Tern Sterna caspia , Gull-billed Tern Sterna nilotica , White-cheecked Tern Sterna repressa and Saunders’s Tern Sterna saunders . These four islands are the most important and sensitive habitat for breeding terns species Sterna sp, Crab Plover Dromas ardeola and Western Reef Heron Egretta gularis in the Persian Gulf. The islands have been identified as an Important Bird Area by Birdlife International proposed for protection as a part of the Mond Protected Area, now part of National Marine Park of Dayer, and suggested for to be classified as sensitive habitat for breeding seabirds.

The enigmatic monotypic crab plover Dromas ardeola is closely related to pratincoles and coursers (Aves, Charadriiformes, Glareolidae)

The phylogenetic placement of the monotypic crab plover Dromasardeola (Aves, Charadriiformes) remains controversial. Phylogenetic analysis of anatomical and behavioral traits using phenetic and cladistic methods of tree inference have resulted in conflicting tree topologies, suggesting a close association of Dromas to members of different suborders and lineages within Charadriiformes. Here, we revisited the issue by applying Bayesian and parsimony methods of tree inference to 2,012 anatomical and 5,183 molecular characters to a set of 22 shorebird genera (including Turnix). Our results suggest that Bayesian analysis of anatomical characters does not resolve the phylogenetic relationship of shorebirds with strong statistical support. In contrast, Bayesian and parsimony tree inference from molecular data provided much stronger support for the phylogenetic relationships within shorebirds, and support a sister relationship of Dromas to Glareolidae (pratincoles and coursers), in agreement with previously published DNA-DNA hybridization studies.

Solar incubation cuts down parental care in a burrow nesting tropical shorebird, the crab plover Dromas ardeola

We describe an unknown mode of solar‐assisted egg development in the crab plover Dromas ardeola, a shorebird that breeds in self‐excavated burrows. The insulating properties of the nest burrow and the intense solar radiation allowed egg development at near‐optimal temperature (35.2°C±0.2) and humidity (60.2%±4.4), allowing a very low incubation attendance by the parent birds (28.3% of time, with recesses lasting up to 58 h). Crab plovers did not abandon completely parental incubation, possibly because of the need to turn their egg, and because the slight warming provided by parents (0.8°C) may improve hatching. This is the first case of solar assisted incubation in a species unrelated to the Megapodiidae, the only birds known to develop their eggs without contact incubation.

Nesting, overwintering, and conservation of the Crab Plover Dromas ardeola in central Eritrea

We describe 30 new nesting sites of the Crab Plover Dromas ardeola, the main breeding grounds of which were largely unknown, and for which fewer than 30 colonies had been confirmed since 1970. Our survey included 90 islands, 53% of those existing, in the Dahlak and Howakil archipelagoes, and off the coast of central Eritrea. Colony size varied between 20 and 400 nests. We estimate the numbers of Crab Plovers breeding in central Eritrea at 5000–6000 pairs, i.e. about 50% of the known world breeding population. We describe two cases of probable replacement clutches, a feature unrecorded in this species. Black Rats Rattus rattus seem unable to open Crab Plover eggs, and do not seem to be a threat. Crab Plover colonies are traditionally exploited by local fishermen for collection of eggs, an activity that has increased recently. Our new records solve only partially the problem of the ‘missing’ colonies that are required to account for the world wintering population of 60 000–80 000 birds, and thus other breeding sites remain to be discovered, probably in southern Eritrea, Sudan and Somalia. We estimated that there are 4800–6500 Crab Plovers overwintering within central Eritrea, making it an important wintering ground for the species.

Post‐migratory care of young by Crab Plovers Dromas ardeola

The Crab Plover Dromas ardeola is the only waterbird species known to provision offspring well after the post‐reproductive migration and through overwintering. A few previous quantitative studies have reported inconclusively that juveniles begged rarely, and also indiscriminately at other juveniles. Here, we describe the feeding behaviour of adult and juvenile Crab Plovers during the first part of the wintering period. Juveniles begged frequently for food, always toward adults, and obtained 0.1 prey items/min from them. Begging birds obtained the largest prey items of those captured by the adults. When foraging alone, juveniles captured prey at the same rate as adults, but captured smaller crabs. The feeding success of adults was not altered by the presence of the begging juvenile. Juveniles depended partly on adults during the first part of the overwintering period, but were almost independent towards the end. Crab Plovers may adopt such unusually prolonged care because they need to abandon their breeding areas quickly, when environmental conditions are extreme. Large numbers of Crab Plovers overwinter in a few areas, now subject to human alteration. Isolated adults may forage on other areas such as narrow and disturbed shores, but juveniles may require wide beaches, suitable for group foraging, that should be considered as key areas for the recruitment of juveniles into the population.

FORAGING BEHAVIOUR OF CRAB PLOVERS DROMAS ARDEOLA AT MIDA CREEK, KENYA

Summary Hockey, P.A.R., Plagényi, É.E., Turpie, J.K. & Phillips, T.E. 1996. Foraging behaviour of Crab Plovers Dromas ardeola at Mida Creek, Kenya. Ostrich 67:33-44. The foraging behaviour of Crab Plovers is directly analogous to the ‘walk-stop-search-walk’ hunting behaviour of true plovers, and changes slightly depending whether the birds are foraging on sand or in water: they are nonterritorial when foraging. Crabs dominate the diet, but other invertebrates and fish are also eaten. Foraging efficiency increases with age and adults and subadults are able to satisfy their daily energy requirements in a single tidal cycle. The population of Crab Plovers at Mida Creek was much larger in 1994 than in 1992, but in 1994 adults achieved much higher intake rates than in 1992, suggesting considerable year-to-year variation in the carrying capacity of Mida Creek for Crab Plovers. The world population of 43–50 000 birds breeds at very few colonies and the species is thus a potential conservation concern. Because of the relative accessibility of large concentrations of Crab Plovers away from the breeding grounds, we suggest that a programme to monitor numbers and population demography should be targeted at nonbreeding aggregations.