Audouin’s Gull in Senegal: status, trends & origin (part I)
When I started birding nearly 30 years ago, Audouin’s Gull was one of those near-mythical birds, endemic to the Mediterranean and listed as an Endangered species on the IUCN Red List. Plus, it’s a real pretty gull, much more attractive than the standard “large white-headed gull”. Fortunately, this highly coastal species has seen substantial increases in its breeding population and has (re)conquered new localities, mostly during the nineties.
It is now found in Portugal (where it didn’t used to breed 30 years ago), Spain (where the bulk of the population breeds), France (Corsica), Morocco, Algeria, Tunisia, Italy, Croatia, Greece, Cyprus, and Turkey. The largest colonies are in the Ebro delta (14,177 in 2007) and the Chafarinas islands off NW Morocco (2,700 pairs in 1997). The Ebro colonies now represent about two thirds of the global population, so it is particularly of note that the species wasn’t even breeding there in 1980: Audouin’s Gull established itself in 1981 when 36 pairs bred, with as many as 4,300 in 1990, +10,000 pairs in 1993… and now certainly more than 15,000 (I didn’t immediately find any recent figures).
The species’ global population is now thought to number 63,900-66,900 individuals, with 21,300-22,300 breeding pairs: to write that this is “a significant increase from an estimated population of 1,000 pairs in 1975” certainly is an understatement… This remarkable feat is thought to be a result of the increased availability of effectively protected areas during the 1980s and of discarded fish from trawlers, particularly around the Ebro delta. Although it may still be vulnerable due to its small number of colonies, it was downlisted to “Least Concern” during the 2015 revision of the Red List, previously being considered Near Threatened (2004), “Lower Risk/conservation dependent” (1994), and Threatened (1988) (IUCN). Quite a conservation success story.
Following a good harvest of ring readings a few weeks ago in the Saloum delta, I wanted to find out a bit more about its history, trends, abundance and distribution in Senegal – and decided to turn it into a blog post here. This wasn’t too difficult given that a ton of research has been done on Audouin’s Gull, resulting in decent knowledge on its population dynamics and structure, distribution, breeding ecology, dispersal, feeding and migratory strategies, etc. The main challenge was to identify the most relevant resources and to distill everything into something relatively concise. And for once there’s even fairly abundant literature on the species in its wintering grounds here in West Africa.
First, let’s have a look at historical records of Audouin’s Gull in Senegal, and see if we can reconstruct the trends for the country.
The ’60s and ’70s – the first records for Senegal
We automatically turn to our rapidly deteriorating copy of Morel & Morel (1994), who only list a handful of records – essentially, the first four records for the country:
An immature collected at Saint-Louis, 11/5/61 and an adult seen on Gorée island (Dakar) on 13/3/64; one photographed at “the entry of the Sine-Saloum” [wherever that may be! I assume near the Saloum river mouth?] on 1/2/75, and one record near Dakar at the end of December 1981.
Dupuy (1984) adds the observation of an adult in the north of the Saloum delta on 13/12/80 but this record was either overlooked, or not retained by M&M. Interestingly, De Smet & Van Gompel (1979) did not encounter the species even though they covered large chunks of the coast between lac Tanma and the western Saloum delta, as well as the Senegal river delta, during the 1978/79 winter. This seems to confirm that Audouin’s Gull at the time was still a rare or very scarce visitor here – something which was about to change very soon.
The ’80s and ’90s – establishment of a wintering tradition
Moving on, Sauvage & Rodwell (1998) consider Audouin’s Gull to be “frequent at PNLB (Langue de Barbarie NP) and Saint-Louis, Jan.-Apr. with max. 17 birds, Jan. 1994, nine ringed in Spain. Up to 10 were wintering around Saint-Louis, 1990-91.” It is “frequent to common Dakar off Pointe des Almadies and Toubab Dialao, Jan.-Mar., max. 104 (four ads.), Toubab Dialao, Jan. 1992. Frequent to abundant Saloum delta. Max. 321 wintering.” The latter figure, obtained in 1985 (Baillon 1989) is significant as it is the first mention of a substantial number of birds in Senegal, and can likely be linked to the “explosion” of the Ebro delta colony. In Jan.-Feb. 1988, Delaporte & Dubois counted gulls all along the Senegambian coast, from the Mauritanian border to Casamance, and counted 81 Audouin’s Gulls (6 near Saint-Louis, 3 along the Petite Cote, 72 around Palmarin) though they estimate a total of 130 birds. They also mention the presence of 185 in the northern Saloum (probably Palmarin/Joal-Fadiout) on 6/12/88. Del Nevo et al. (1994) conducted counts in February 1991 and in September-October 1992, noting a total of 459 birds in Senegal and 72 in Gambia (1991), and 276 in Senegal the following year, mainly at Sangomar and Joal-Fadiouth.
A few eBird records from the early nineties provide some more context for that decade, in particular the count of no less than 470 birds at the Somone lagoon on 28/2/91, with two at Mbodiene (south of Mbour) a couple of days earlier, and 12 at Plage de Hann (Dakar) on 18/2/91 (O. Benoist). Bengtsson (1995) reports a minimum of 456 near Palmarin in Nov.-Dec. 1994. Based on these records, it looks like the species became a regular winter visitor to Senegal in the early to mid ’80s, and rapidly established a number of traditional wintering areas during that decade.
The next comprehensive figures are reported by Schepers et al. (1998) based on waterbird counts from January 1997 in the Saloum delta and along the Petite Côte. The team counted a total of 858 Audouin’s Gulls between Dakar and the delta, with the majority (673) found in the Saloum, and 185 along the Petite Côte. They estimated the wintering population to number around 1,000 birds, while in 1988 the same areas (incl. Saint-Louis) held at least 80, but more likely at least 130 Audouin’s Gulls (Delaporte & Dubois 1990, though Baillon & Dubois in 1991 estimated the number of wintering birds to be around 500, without providing further details). Regardless, these numbers suggest that Ichtyaetus audouini continued to increase in numbers throughout the late eighties and nineties, and confirmed that Senegal plays an important role for the species during its non-breeding cycle.
2000 – 2017 – stability
Fast-forward a few years to the first decade of the 21st century: hardly any published data! The only citations of the species that I could find are from seawatch sessions and a few trip reports. For instance from 2006, when a Swedish team counted migrating birds off Ngor, from 10–14 and 25–26 November: 28 Audouin’s Gulls were noted on three separate days (Strandberg & Olofsson 2007). A year later, a more comprehensive migration study at Ngor, with impressive numbers of seabirds counted from 5-28 October, resulted in a total of 692 birds. In the Senegal delta, a maximum of c.15 birds were counted in 2002 (Triplet et al. 2014).
In January 2011, some 50 Audouin’s Gulls were counted by Ottvall et al. at Lac Rose, providing “more evidence of the increasing numbers […] wintering along the coast north of Dakar.” Later that year, Paul Robinson reports two 2nd calendar years from Lac Tanma, which seems to be the first mention of the species here (I’ve seen two birds on 28/8/16 here, but not during other visits in 2015-17). Paul also recorded the species in Popenguine, where on 12/2/12 the pond had “a few” Audouin’s gulls amongst the gulls.
In July 2012, Paul counted c.150 Audouin’s Gulls at Technopole, noting that these were “all sub-adult birds from 2010 and 2011, represents a real increase in summering birds south of the Sahara and a West African summer record count. Several had Spanish rings.” Indeed, Audouin’s Gull can now be seen year-round in Senegal.
Ngoné and colleagues estimated the Palmarin “winter” population to number 445 individuals (278 adults, 167 immatures) based on the modelling they performed on their monthly counts and ring recoveries from the end of 2013 up to end 2015. This seems rather on the low end given that at peak times in October they recorded up to around 700 birds, and that in recent years it’s easy to find more than 300 birds together in the lagoons along the Samba Dia road – surely there are many others scattered throughout the western Saloum delta, e.g. around Sangomar and further south. More on the findings of their study, which was presented under the form of a poster at last year’s PAOC, will be discussed further down.
Current distribution in Senegal
The winter range of the species in Senegal probably hasn’t changed much in the last 20-30 years, with the following areas being regularly used by Audouin’s Gulls:
- La Grande Côte: Langue de Barbarie and elsewhere in the Senegal delta around Saint-Louis (shores, beach and lagoons), though never in large numbers, with a maximum of c.65 birds in Jan. 2013 (Triplet et al. 2014). On the southern end of the coast, the species is regularly seen at Lac Rose and sometimes at Lac Tanma. It probably also occurs along the beach throughout (I need to ask Wim about this!), especially around the larger fishing towns and villages: Kayar, Mboro, Lompoul, etc. At Lac Rose, ca. 350 birds were seen on 11/2/18, suggesting that this is still an important roosting site for the species, at least during part of the northern winter.
- Cap-Vert peninsula: Regular at Lac Rose (e.g. c.60 on 8/8/15, 2 on the beach on 22/1/17, 5 on 14/5/17) and Technopole, where most numerous in January-March, but records from all months except for September (when I rarely visit Technopole); so far my highest count has been a modest 50 birds on 12/3/17. Birds are also regularly seen from Ngor, either migrating or, more often, feeding out at sea. In autumn and winter, one should be able to see Audouin’s Gull pretty much all along the coast from the Pointe des Almadies along Yoff all the way to Lac Rose. I really need to check out the Hann bay from time to time, as there are often lots of gulls and terns. The species has also been reported from Yene-Bargny where is likely still a regular visitor, and may well be numerous at times (in autumn maybe? Birds may favour Technopole later in winter).
- La Petite Côte: the Somone lagoon seems to be the most regular site, but birds also show up at least irregularly at Popenguine and Mbodiene, and likely feeds off-shore along the entire coast here.
- Saloum delta: this is of course the main wintering area, that likely holds about 80% of the Senegalese wintering population. Birds are typically concentrated in the lagoons to the north of Palmarin, and do not gather far inland. It should also occur further south in the delta but I have no data from there.
- Coastal Casamance: the only record I know of is of two birds on 12/10/16 flying north along the beach at Diembering. There certainly are more records (though none on eBird nor observado.org) as Casamance must be the far end of their regular range, given the absence of sightings in nearby Guinea-Bissau.
In terms of population size, my own conservative guestimate puts the current number on 800-1,000 birds, so not any different than the 1,000 birds estimated to winter in Senegal in January 1997, which logically reflects the species’ stable global population trend.
Elsewhere in West Africa
Isenmann et al. (2010) enumerate lots of records for Mauritania, but little or no info is provided on the evolution of the wintering population in the country, probably because of a lack of historical data. The current status is that of a regular migrant and wintering bird, with at least several hundreds of birds along the coast. Far more birds are said to winter along the Western Sahara coastline. The Gambia is also part of its regular winter range, mainly on and around the Bijol Islands, Tanji Bird Reserve. In 2007/08, about 500 Audouin’s Gulls were counted there. The first Gambian record, as per Morel & Morel, is of a bird at the Bakau Lagoon on 21/2/82.
Surprisingly, the species hasn’t yet been seen in Guinea-Bissau, which is most likely right outside the regular winter area, but surely a few individuals must reach the NW corner of the country, and particularly the Bijagos, given that they are recorded at least from time to time (it would seem) in Casamance and that Gambia is less than a 100 km away from the border. My Oct. 2016 observation near Diembering was barely 20 km from the border and both birds were moving north… In Guinea, the first record was obtained just last year by gull expert Peter Adriaens, a first-winter near Cap Verga on 28/10. The lack of other records from Guinea (and Guinea-Bissau) most likely reflects the absence of observers in the country, rather than a real absence of Audouin’s Gull which surely must at least from time to time reach Guinean waters. This is not the case in relatively well-watched Ghana, where the species is a true vagrant: a first-winter on 13/1/14 was quite an unexpected first for the country, as it had not previously been reported south of Senegambia (Kelly et al. 2014). [note that the species certainly doesn’t winter in Gabon, contra BirdLife International’s species fact sheet].
Now, I still wanted to talk about the origin of wintering birds in Senegal and summarise current knowledge based on ringing recoveries, but my blog post is already getting a bit long… that part will have to wait for a second installment, hopefully a week or two from now.