FAUNA
FAUNA
Over-summering birds
in San Quintín Bay
By Jonathan Vargas and Estefanía Muñoz
Long-billed Curlews (Numenius
americanus) near the oyster farms in
San Quintín Bay. Photo: Jonathan Vargas.
Some individuals spend the summer
in their wintering sites instead of
migrating long distances.
S
urely one of the most amazing natural phe-
nomena is bird migration. This event allows
us to witness the migration of thousands of ani-
mals that travel long distances to find better
conditions to survive and breed.
Migration represents a great challenge and
many species die in the attempt, since a lot of
energy is spent. Nevertheless, the survival ins-
tinct is greater than any adversity, and bree-
ding is one of the main drivers for migratory
birds.
Although not all birds migrate, the majority of
birds fly to their breeding grounds in the north
or their wintering grounds in the south. Also,
not all individuals need to migrate long dis-
tances and some of them spend the summer in
their wintering grounds. These individuals are
known as over-summering birds.
For some years it has been known that
over-summering behavior occurs generally in
the first year of life of migratory shorebirds.
The farther away the breeding grounds are lo-
cated, the more likely it is that birds will over
summer.
It has been documented that over-summering
birds can spend from 19 to 31 months on the
grounds where they spend the winter, before
migrating to their breeding grounds for the first
time to find a mate. But generally, second-year
individuals become old enough to breed and
migrate north for the first time.
Even though this behavior is common among
shorebirds, it is also found on one of the most
representative birds in San Quintín Bay, the
Black Brant (Branta bernicla nigricans).
important location for the Black Brant, since it
hosts between 30 and 50% of the worldwide po-
pulation, that is, around 30,000 brants each year
during winter migration.
Around this time, some over-summering birds can
be found in the bay, like the Black Brant and the
Lesser Scaup (Aythya affinis), both species are mi-
gratory and they are generally observed during
the winter migration.
The same way, the Black-necked Grebe (Podiceps
nigricollis) is a species seen in large numbers
during winter, nevertheless, during summer it is
Also known as the Pacific Black Brant, this
species travels each year from the breeding
grounds in the north to the wetlands in nor-
thwestern Mexico, and San Quintín Bay is an
possible to find a few, this is due to the over-sum-
mering individuals.
Even on the coast, small groups of other spe-
cies such as the Surf Scoter (Melanitta perspi-
cillata) and the Western Grebe (Aechmophorus
occidentalis) can be seen feeding near the wa-
ves. Surely these over-summering bird will soon
migrate to breed.
All of this reflects the importance of San Quintín
Bay for migratory birds, not only in the winter
but also during summer. This location is so im-
portant, that breeding birds can be found during
summer, species like the Snowy Plover (Chara-
drius nivosus), the Black Skimmer (Rynchops
niger) and the Least Tern (Sternula antillarum).
These three species are considered a priority for
conservation and breed on sandy beaches and
marshals during summer.
Because of this, at Terra Peninsular we are
committed to conserve and protect the natural
ecosystems and wildlife of the peninsula of Baja
California, so we can continue enjoying such ad-
mirable events as bird migration.
Surf Scoters (Melanitta perspicillata) at
La Chorera beach, in San Quintín.
Photo: Jonathan Vargas.
References
19 MEDITERRANEWS
Black Brants wintering in the bay.
Photo: Alan Harper.
Berlanga, H., H. Gómez de Silva, V.M, Vargas-Canales, V. Rodríguez-Contreras, L.A.
Sánchez González, R. Ortega-Álvarez y R. Calderón-Parra. 2015. Aves de México:
Lista actualizada de especies y nombres comunes. CONABIO, México D.F
JUNE 2017 20