Dehalak Archipelago and offshore islands

Country/territory: Eritrea

IBA Criteria met: A1, A3, A4i (2001)
For more information about IBA criteria please click here

Area: 300,000 ha

Site description
The Dehalak Archipelago consists of a group of about 220 islands, ranging from minute to very large, lying in the Red Sea east of Massawa, from about 20 km to more than 100 km offshore. The islands vary from sandbars to complex ecosystems comparable to those on the nearby mainland, with complexity increasing with size and proximity to the shore. Most of the islands are composed of salt diapir, which consists of salt deposits 3 km deep, formed when the Red Sea almost totally dried out many aeons ago. These are now expanding as they get wet, and rising upwards; where they reach the photic zone (50 m below the sea surface) corals start to develop. As the deposits continue to rise into shallower waters, the corals die off and islands are formed as the deposits rise into the air or are forced up by periodic tectonic movements. The largest island, Dehalak Kebir, covers 64,500 ha and is the most complex ecologically, with three different levels of uplifted corals. Other islands are composed of Pleistocene limestones and marine sand deposits.

To the south there are other smaller groups of islands that are also included within the proposed IBA, although there are few specific bird records from these other groups. These are the continental islands just offshore and south of the Buri peninsula in Mersa Fatmah Bay, and a few offshore at Asseb, one of which, Senahor, is volcanic in origin. The areas of sea between the islands within these groups and between the main groups and the mainland (particularly the Massawa channel between the Dehalak Archipelago and Massawa) should probably also be included, although there are few specific bird records from these inter-island areas. Records from the immediate offshore islands, including Batsii (Massawa), Taulud and Sheik Said (Green) Islands are included in the Massawa Coast account (see ER005). More survey work will be required to determine the boundaries of one or more IBAs covering the areas of most importance to bird populations using the various groups of islands and the surrounding seas.

The majority of the islands consist of bare sand, some with exposed uplifted coral and very sparse scrub and grassland vegetation similar to that on the adjacent mainland (e.g. Acacia, Panicum, Sargassum and Euphorbia spp., with Suaeda, Statice, Atriplex and Zygophyllum spp. on low areas of saline sand). Some of the islands have areas of rocky cliffs, some have sand, pebble or mudflats and there are also large mangrove swamps (principally Avicennia marina, with some Rhizophora and Ceriops spp.) on some islands in the Dehalak and Asseb Bay groups. There is a tidal range of between 50–120 cm. Both day and night-time temperatures are high (40–50°C) and there is very high humidity, but only about six islands, all in the Dehalak archipelago, have surface fresh water. Almost all the 180–250 mm of rainfall falls between October and May.

Dehalak Kebir island was used as an Ethiopian military base against Eritrean rebels during the war. Apart from this, fishermen and people keeping goats inhabit a few islands. There is also some very low-key tourism (administered by the Ministries of Tourism and Fisheries) on Dehalak Kebir, based largely on the attractions of diving in the Red Sea and around the coral reefs.

Key biodiversity
See Box and Table 2 for key species. Most rocky islands with some cliff edges in the Dehalak Archipelago have several pairs of Falco naumanni. Larus leucophthalmus was said to be a ‘very common colonial breeding bird’, with maximum reported numbers of 1,393 adults, eight immatures and 227 young on 10 islands in 1962, and more recent observations which confirm this level of abundance (e.g. 200 adults on Harat Island in 2000) (Kahsai pers. comm.). Emberiza cineracea was ‘seen often on the [Dehalak] islands, provided they were rocky and had some vegetation, even far offshore’ in the 1990s (C. Hillman pers. comm.). Circus macrourus is also said to occur. The Sahara–Sindian (A02) biome species Falco concolor is recorded from only one other site in Eritrea and the Dehalak Archipelago is a stronghold for this species (the most recent records are from Harat Island). It breeds on several islands (more than 170 pairs have been recorded) and is said to feed almost entirely on Palearctic migrants. Three Sahel (A03) biome species are also recorded, including breeding Ardeotis arabs and Streptopelia roseogrisea (although this latter record is rejected by some authors; Hillman pers. comm.). One Sudan–Guinea Savanna (A04) biome species, Falco alopex, has been recorded from the Dehalak Archipelago, but was presumed to be a vagrant from the mainland. One Somali–Masai (A08) species, Ploceus galbula, also occurs on the Dehalak islands; see Table 2.

The Archipelago is famed for its seabird colonies: ‘the great colonies of breeding seabirds in summer’ recorded by Heuglin in the nineteenth century and commented on by Smith nearly 100 years later. The islands are also directly on the flyway for Palearctic migrant waterbirds and terrestrial species, which use them for feeding, rest and shelter in very large numbers (Hillman pers. comm.). There are very few data on numbers or movements, but it seems likely that, in addition to acting as staging-post for north–south migrations, the islands’ location, between Africa and the Arabian peninsula, makes them significant as an east–west stepping-stone between Africa and Asia. Most of the count data are from surveys in the 1960s. There is no reason to suppose that numbers should have declined since then and these counts will in most cases have been considerable underestimates of total population sizes since only a few (and generally the most accessible) islands were visited in each case. Most of the seabirds are reported as breeding in the hotter ‘summer’ months (from May to October), but other species (colonial waterbirds, raptors, passerines) have been found breeding in ‘winter’ (December to May) after or during the winter rains.

There are very large numbers of breeding and wintering gulls and terns. Both Larus leucophthalmus and L. hemprichii are recorded breeding on most of the Dehalak islands visited to date. Numbers of L. hemprichii probably exceed the IBA threshold for this species: in 1962, c.90 adults were counted on one island and the species was ‘common’ on other islands visited. In 2000, up to 300 adults were recorded on Harat island (Kahsai pers. comm.). Sterna bengalensis breeds in thousands, with ‘several thousand pulli’ reported in 1962 and a large colony of over 1,000 adults on Harat Island in 2000 (Kahsai pers. comm.). S. repressa is also ‘common’ breeding and S. anaethetus is reported almost certainly breeding in the Asseb islands as well as in the Dehalak group (a total of 950 birds recorded on the Dehalak islands in 1962). S. bergii was recorded breeding by Heuglin in the 1850s. Larus ridibundus overwinters and there are reports of ‘abundant’ Larus fuscus and ‘common’ Sterna caspia (both in March). Other species recorded breeding on the Dehalak islands in significant numbers (which may well exceed IBA thresholds with further survey work) include Phaethon aethereus (breeding and ‘fairly common offshore (post-breeding)’), Pelecanus rufescens, Sula leucogaster (breeding ‘in their hundreds on several taller coral ‘islands’ (including Harat, 50 adults) in late ‘summer”) and Dromas ardeola (‘flocks of 20–30 on shorelines of all islands visited’ and ‘frequent on the shores of the islands’, with two known breeding colonies on two far offshore islands: Hillman pers. comm., Kahsai pers. comm.).

A variety of other waterbirds occur, in limited numbers, where there is suitable habitat. These include Egretta gularis, Ardea goliath, A. purpurea, Butorides striatus, Threskiornis aethiopicus (breeding), Platalea leucorodia and P. alba. Rynchops flavirostris occurs, as do a variety of Charadrius spp., Tringa spp. and other waders.

The islands also support very significant numbers of breeding Pandion haliaetus, with an estimated potential breeding population of more than 300 pairs (Fisher pers. comm.), and possibly into the thousands (Hillman pers. comm.). Other raptors recorded include ‘abundant’ wintering Milvus migrans (recorded both from the Dehalak islands and from the Massawa sea channel), Neophron percnopterus (on Nocra and Dehalak island groups), Circus aeruginosus, C. pygargus and (breeding) Falco peregrinus. Migrant passerines include Riparia riparia, Hirundo rustica and Motacilla flava.

Non-bird biodiversity: The waters off the Eritrean coastline and around the Dehalak archipelago support several hundred (and probably thousands) of fish species, many of which breed in and around the coral reefs. Some such as anchovies, sardines and tuna were, in the past, fished commercially and these and other species also form the food-supply for breeding seabirds, ospreys, etc. Five species of sea-turtle are recorded from Eritrean waters, including breeding Chelonia mydas (EN) and Eretmochelys imbricata (CR) in the Dehalak archipelago. Also reported from ‘the Eritrean coast’ (and hence probably within the proposed IBA), but with no information on location or numbers are Dugong dugon (VU) and ‘dolphins, porpoises and whales’. Smith reports small schools of Physeter macrocephalus roaming around the Dahlak Archipelago, ‘accompanied by vast flocks of seabirds’ and ‘disturbing the marine life’ (Smith 1953). Yalden et al. (1996) list Globicephala macrorhynchus (LR/cd), Delphinus delphis and Physeter catodon (VU) from Eritrean waters. Gazelles are reported from Dehalak Kebir and Nocra—dwarf Gazella soemmerringii (VU) of uncertain taxonomic status, probably hybrids of species introduced in earlier years. Reports in the literature of the presence of Oryx beisa on the Dehalak islands appear to have no foundation.

Recommended citation
BirdLife International (2023) Important Bird Areas factsheet: Dehalak Archipelago and offshore islands. Downloaded from on 06/02/2023.