P•CBA

P·CBA

P·CBB

P·CBC

Hybrid gulls ringed at Texel in summer 2006:

a request for reports of sightings to document winter dispersal and migratory movements,

plus photographs to study plumage development with age

A mixed pair Herring Gull (♂) × Lesser Black-backed Gull (♀) successfully reared three chicks in the Kelderhuispolder

colony at Texel (Wadden Sea islands, The Netherlands) in summer 2006. By chance, the pair was found in one

of the enclosures erected to document breeding success in Lesser Black-backed Gulls. The fact that one of the nests

actually contained a mixed pair was discovered much later, some weeks prior to fledging, when the chicks developed

confusing external (plumage) characteristics and were fed a mixed diet of prey typical for Herring Gulls and

Lesser Black-backed Gulls respectively.


Nest when found, 6 May 2006		Both adults in enclosure, 17 June 2006

Egg 1, 67.41 × 47.22 mm Found 6 May, Hatched 1 June	Egg 2, 68.82 × 47.71 mm Found 6 May, Hatched 2 June		Egg 3, 64.42 × 46.91 mm Found 9 May, Hatched 3 June

The nest was found in a grassy part of a large Lesser Black-backed Gull colony and with two eggs

on 6 May 2006 at 53°0.551’N, 4°43.086’E. It was one of the earlier attempts in an otherwise very late season.

On 9 May 2006, the clutch was complete and incubation commenced.

When it was discovered that a mixed pair was involved, the three chicks were photographed at regular intervals to

document their plumage (mainly mantle and wing). Growth was monitored (3-day intervals) and the food

was studied by sampling pellets and chickfeed within the enclosure. Blood samples were taken of the chicks

for DNA analysis.

	PCBA
	PCBB
	PCBC
Upper wing patterns of chicks colour ringed PCBA, PCBB and PCBC just prior to fledging

The pair was successful and raised three chicks. The chicks were ringed (tibia, steel) and colour ringed

(tarsus, green) just prior to fledging. The colour rings are as follows:

P·CBA

Largest pullus, hatched

1 June, body mass

800-900g early July

2006

Steel ring:

Arnhem 5416529

P·CBB

Second-largest pullus,

hatched 2 June, body mass

600-700g early July

2006

Steel ring:

Arnhem 5416530

P·CBC

Smallest pullus,

Hatched 3 June, body mass 600-700g early July 2006

Steel ring:

Arnhem 5416528

The text is repeated three times on each ring and the colour ring is 34mm high. We are interested not only

to study the development of the plumage and the dispersal of these hybrids, but also their foraging habits and feeding areas.

Smallest pullus,

Hatched 3 June, body mass 600-700g early July 2006

P·CBC

Steel ring:

Arnhem 5416528

Please report the following data for each sighting:

· Date and time

· Place (preferably with geographical co-ordinates)

· Observer, name and (e-mail) address

· Type of area (e.g. potential as feeding site)

· Behaviour of the bird (with emphasis on foraging behaviour)

· Condition of the bird

· Condition of the ring

And when you find the bird dead…we are desperate to receive the corpse for autopsy and further investigations!

Please contact:

Kees Camphuysen

Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg Texel, The Netherlands

+ 31 222 369488 (office hours), + 31 222 318744 (other hours)

kees.camphuysen@ wxs.nl or camphuys@ nioz.nl