To understand the post-breeding migration of aquatic birds utilizing the
western Atlantic flyway along the coastal region of Souss Massa Draa, the
phenology of these species and the importance of this migration route, we
carried out surveys in the mouths of the three main rivers basins of the region.
We carried out the study within the limits of Souss Massa National Park, specifically
in the mouths of the rivers Oued Massa and Oued Souss, both of which are
located in the province of Agadir, Morocco.
Methodology
We focused our surveys in coastal or riverine habitats, normally during
low tide to take advantage of exposed beaches, islands and shores. This allowed
us to count all of the birds using a 20x60 spotting scope and 8x and 10x
binoculars. We conducted our counts from established observation points,
normally from elevated spots, which allowed for a clear view of the river mouth.
Observations were recorded onto data sheets. All observed aquatic birds were
counted except for members of the Laridae
family and Bubulcus ibis.
During the post-breeding migration period of 2013 we carried out one
census per week for a total of 14 surveys, as weather permitted. The active
migration period in this zone of the Atlantic flyway is between 15 August and
15 November. During that time we calculated the total accumulated abundance,
the abundance of each species and the species diversity of each area. For a
more accurate analysis, we grouped distinct species into sets with similar
ecological characteristics.
Results and conclusions
Between Oued Massa and Oued Souss we counted a total of 7.502 birds and
53 species corresponding to 13 families. Of these, 3.756 birds, corresponding
to 13 families, were counted in Oued Massa and 3.746 birds, representing 11
families, were counted in Oued Souss. The most represented family in both
locations was Scolopacidade, with a total of 2.393 birds and 16 species. In the
mouth of the Oued Souss, this family represented 24,40% of the total recorded,
with 14 species and 914 individuals. In the mouth of Oued Massa, this family
represented 39,38% of the total recorded abundance with 16 species and 1.479
individuals.
The abundance of birds has varied in both locations, which indicates a
continuous turnover of birds. This could imply that the coast of Souss Massa is
a place of high importance within the Atlantic flyway. Both Oued Souss and Oued
Massa function as stopover points and feeding stations between the breeding and
wintering grounds. The abundance of the Oued Massa has fluctuated between 122
and 494 birds and in the Oued Souss between 114 and 558 birds. The most
abundant family in the Oued Massa was Scolopacidade
with 1.479 birds, followed by Charadridae,
which was the dominant shorebird family in this location, with 712 individuals.
However, in Ouedd Souss the most abundant family was Phoenicopteridae with 985 individuals, followed by Scolopacidae with 914 individuals.
In the mouth of Oued Massa the most abundant
species during the post-breeding season was Calidris
alpina with 924 individuals, corresponding to 24.60% of the total recorded
abundance, followed by Charadrius
hiaticula with 466 individuals, representing 12.41% of the total recorded
abundance, and Phoenicopterus roseus
with 265 individuals, or 7.06% of the total abundance. In the mouth of Oued
Souss, the three most abundant species were the same as those in Oued Massa,
although in different percentages. Phoenicopterus
roseus was the most abundant with 985 individuals, or 26.29% of the TRA,
followed by Charadrius hiaticula, with
427 individuals, or 11.40% of the TRA and Calidris
alpina with 353 individuals, representing 9.42% of the TRA.
During the middle of September an
increase in abundance occurs in both locations. This could coincide with the
passage of long distance migratory birds such as Calidris alpina, Charadrius hiaticula, Calidris ferruginea, Limosa
lapponica and Platalea leucorhodia.
Towards the end of October and early November another peak in abundance occurs
which may be related to the arrival of wintering species such as anatidae, Anas clypeata, and A. Acuta, as well as other species such
as Phoenicopterus roseus and Phalacrocorax carbo.
For this study, we grouped those species
that share similar ecological characteristics together. Five groups were
present in both locations (divers, herons, ducks and rails, waders and gulls
and terns). Waders and herons were the principal groups represented with a
total of 85.69% of the total number of birds in Oued Massa and 87,94% in Oued
Souss. In Oued Massa the best represented group was the waders, representing 60,2%
of the birds detected during the study period, followed by herons with 25, 49%.
However, in Oued Souss the herons were slightly better represented, comprising 45,48%
of the total birds observed compared to the waders with 42.45% of the total
abundance. The rest of the groups had quantifiably fewer numbers, except for
the ducks in Oued Massa during the end of the migratory period.
The
highest diversity occurred during the last two weeks in August and the
beginning of September - the first weeks of migration. At this time the first
long distance migrants coming from northern Europe begin to arrive. They may
join the non-breeding birds that spend the summer in the region. During the
rest of the study the biodiversity was variable, with a slight increase during
the second half of October and beginning of November, coinciding with the
arrival of wintering birds.
A review of the existing
bibliographical information shows the decline of some migratory species,
principally those from northern Europe that winter north of the Sahara – their
southern limit. These include Grus grus,
Vanellus vanellus, Numenius arquata and Pluvialis
apricaria. These species are rarely seen nowadays and this could be related
to global environmental changes.
References
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