Giuseppe De Marchi

Sex Discrimination of Crab Plovers (Dromas ardeola) by Morphometric Traits

Abstract. Determining the sex of Crab Plovers (Dromas ardeola) based on morphology has, hitherto, proven difficult. Here, six morphological traits (head-bill length, bill length, bill depth, wing chord, tarsus length and weight) of 39 molecularly or behaviorally sexed breeding Crab Plovers were compared in order to find a reliable morphometric way to determine their sex. Males were significantly larger than females in all traits, except tarsus length, and especially in traits related to head and bill size, where males were 6.8 to 11.4% larger than females. Discriminant Function Analysis correctly classified 97.4% of birds using only bill depth and bill length, providing an efficient tool for sexing Crab Plovers in the hand.

Breeding Biology of the Crab Plover (Dromas ardeola) on the Mond Islands, Northern Persian Gulf, Iran

Abstract. The present study describes the breeding biology of Crab Plovers (Dromas ardeola), a little-known shorebird species nesting on Nakhilu and Omol-Karam Islands located in the Nakhilu Marine National Park in the northern Persian Gulf, Iran. This study occurred during the breeding seasons of 2009–2011. Colonies had between 500–1,500 nests and were located on sand banks 1–3 m higher than the surrounding ground in non-overlapping areas. Burrow digging began in mid-April, and single nests were built in 2.82 ± 0.1 days (Range = 2–4 days, n = 45) in a period of 10.5 ± 0.76 days (Range = 8–13 days, n = 6), although a spread of digging and laying of 87.50 ± 2.96 days (Range = 82–94 days, n = 4) was recorded primarily due to renesting after human damage to the burrows. Range in nest densities was 0.14–0.26 nest per m2. The clutch size was 1.01 ± 0.005 (Range = 1-2, n = 421). Egg size (n = 47) was 64.05 × 44.04 mm with an average incubation period of 33 days (Range = 31–35, n = 21). Hatching success was 63–81%, with failures primarily due to egg collecting by local fishermen and tourists. An estimated of 7 weeks passed between hatching and fledging. Fledglings had almost fully developed wings (83% of adult wing length) and feathers, but very low weight (about 55% of adult weight) and smaller bill length (only 60% of adult bill length). A stronger control of visitors and local fishermen would benefit the breeding population of Crab Plovers on the islands.

Coloniality in the Crab Plover Dromas ardeola does not Depend on Nest Site Limitation

Abstract. The Crab Plover (Dromas ardeola) is a little-known shorebird that breeds colonially in self-dug burrows on islands in the north-western Indian Ocean. To test whether the “nest site limitation” hypothesis could satisfactorily explain the high nest density in this species, 21 colonies were studied in Eritrea from 2002 to 2009. The hypothesis was falsified by the following observations: across the study period, nesting colonies were relocated on the same sandbanks every year and most occupied no more than 4% of the area suitable for excavating burrows; colony size and area suitable for burrowing were not correlated; nest density and colony size were not significantly correlated; the area occupied by nests increased steadily throughout the nest-building period; nests were closely-spaced throughout the building phase rather than being scattered throughout the area eventually used for digging. These results indicate that the Crab Plover is not site-limited but a truly colonial species.

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.

Fishes in the desert: mitochondrial variation and phylogeography of Danakilia (Actinopterygii: Cichlidae) and Aphanius (Actinopterygii: Cyprinodontidae) in the Danakil Depression of northeastern Africa

Abstract The Danakil Depression in northeastern Africa represents one of the harshest arid environments on Earth, yet two genera of fishes, Danakilia (Cichlidae) and Aphanius (Cyprinodontidae), share its sparse aquatic habitats. The evolutionary history of these fishes is investigated here in the context of genetic, geological and paleoenvironmental information. We collected samples from seven sites and assessed phylogeographic relationships using concatenated COI and cytb mtDNA genes. Danakilia morphospecies show low differentiation at mitochondrial markers, but variation is partitioned between a northern cluster containing D. dinicolai plus three undescribed riverine populations, and a southern cluster including two creek populations of D. franchettii separated by the hypersaline waters of Lake Afrera. Aphanius displayed four genetically distinct clades (A. stiassnyae in Lake Afrera; one distributed across the entire area; one in Lake Abaeded; and one in the Shukoray River), but without clear large-scale geographic structure. However, Danakil Aphanius are clearly differentiated from A. dispar sensu stricto from the Sinai Peninsula. Geological evidence suggests that after the Late Pleistocene closure of the Danakil-Red Sea connection, increased post-glacial groundwater availability caused the formation of a brackish paleo-lake flooding the entire region below the –50 m contour. Fish populations previously isolated in coastal oases during glaciation were able to mix in the paleo-lake. Subsequently, in a more arid phase starting ∼7300 BP, paleo-lake regression isolated fishes in separate drainages, triggering their still ongoing diversification.

A Modified Leg-noose Trap for Crab-plovers (Dromas ardeola) at Burrow Nests

ABSTRACT Being trapped is a potentially stressful experience, especially for breeding birds, so capture should be limited to target individuals and be as least harmful as possible. We describe here a modified leg-noose trap that we developed for the burrow nesting Crab-plover (Dromas ardeola). Similar to other commonly used devices, it consists of monofilament fishing line nooses secured to a heavy metal base. We modified this traditional device by positioning the nooses perpendicular to the bird movement and by adding shock-absorbing elastic bands. This last addition proved effective in protecting the captured birds legs from superficial wounds and abrasions; it did not affect capture success relative to a version of the same trap lacking these improvements. Such improvements could be applied to similar noose traps employed for other birds in order to reduce discomfort and avoid injury.