COTTAAR F, VAN KLEINWEE M & VERBEEK-COTTAAR J (2019) Mixed breeding pair Herring Gull Larus argentatus x Lesser Black-backed Gull Larus fuscus. LIMOSA 92 (2): 95-99.
In May 2017, a male Herring Gull was seen together with
a female Lesser Black-backed Gull in the gull colony of
IJmuiden, the Netherlands. The male had colour-rings green
Y.CBC, the female was later colour-ringed with combination
green Y.CHA. At the time of the first observation the pair
was showing pair bonding behaviour: the male was feeding
the female. During the breeding season the pair built a
nest and incubated three eggs of which one egg hatched.
Unfortunately, the chick only survived for a week. In the
previous breeding season the male Herring Gull had been
paired with a female (unringed) Herring Gull. Possible
reasons to pair up with a female Lesser Black-backed Gull
in 2017 include (1) voluntary switching to a new partner
because of a previously unsuccessful breeding attempt, (2)
forced switching because a previous partner does not return
(deceased), (3) a partner is 'claimed' by a third individual, or
(4) a shortage of partners of the same species (females of
large gulls often breed in a colony different than the colony
in which they are born). Although the reason for the peculiar
mate choice remains unclear, a shortage of Herring Gulls
in the colony could have made the male decide to switch
to a Lesser Black-backed Gull. From the viewpoint of the
female Lesser Black-backed Gull the decision to pair up
with a male Herring Gull is intriguing because of the large
number of Lesser Black-backed Gulls available in the colony.
Documented observations of mixed pairs of Herring Gull x
Lesser Black-backed Gull are rare. This was only the second
case a mixed breeding pair was discovered in our well-studied gull colony.
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