Anleitung zur Brutbestandserfassung von ... - BLMP Online

Anleitung zur Brutbestandserfassung von Küstenvögeln im Wattenmeerbereich - 47 -
colonies. Other factors should only be used if exact information on attendance etc.is
available for a given colony. Alternative factors should always be documented. At present
such information is only available for a few colonies in the Wadden Sea.
D-Counts of nests in gull colonies (one count before hatching). Such counts should only be
carried out if other breeding species are not endangered by the count and should not be
carried out in mixed colonies with terns or Avocets. In order to prevent double counts of
the same nest the counted nests should be marked with sea shells or other small objects
or two parallel strings, which can be moved gradually through the colony, should be
used to divide the colony into easily countable strips.
The populations of waders which breed more or less singly should be assessed using a
simple survey of territorial pairs (method E). Territorial behaviour of waders is not as noticable
as that of most passerines and has, up to now, not been defined sufficiently. Breeding
Oystercatchers only show territorial behaviour during 10% of the time they are in the
breeding area, at least three quarters of the day they simply stand still in their territory and
many birds do not even show territorial behaviour when disturbed.
The results of counts of territorial pairs have, in the past, thus been greatly effected by the
experience of the counters and how stringently they applied previous standards. On the
basis of present knowledge and experience of the breeding biology of the birds concerned
and of the occurance of non-breeders during the breeding season, the behavioural
traits which, as a minimum, should be recorded if a bird or birds are to be classed as a
territorial pair have been specified in this report.
With most species all sexually mature individuals present in the breeding area, with the
exception of flocks of roosting non-breeders, should be taken into consideration when assessing
the number of territorial pairs in a given area. The only decision that has to be
made is if two birds, that are not sitting or standing directly side by side, are a pair or parts
of two pairs. In breeding sites with high concentrations of breeding pairs, birds flying and
uttering anxiety calls also have to be counted. In such cases the number of birds counted
should be multiplied by 0.7, as with method C for colony breeding birds (e.g. Oystercatcher
and Lapwing). With the Redshank, however, the factor is much higher and for this
species only the number of individuals should be reported.
With a few species large numbers of non-breeders are present during the breeding
season which are not easily identified as such. In such cases the observation of courtship
and display, and agitated behaviour or anxiety calls from adults (criterien 5 and 7 of the
codes of the European Atlas of Breeding Birds of the International Bird Census Committee
EOAC) are a prerequisite for the evaluation of territorial pairs. This applies also for
single pairs of all colony breeding birds, with the exception of the Kentish Plover.
In the census areas of the Joint Monitoring Program for Breeding Birds in the Wadden
Sea the number of individuals (sum of all sexually mature single birds, birds standing in
pairs and in small groups of up to 6 birds; method F) should be recorded in addition to the
number of territorial pairs. These values are less susceptible to individual counting error
and are probably more suitable for the assessment of population trends than are the numbers
of territorial pairs. In addition large flocks of non-breeding birds should also be assessed,
at least in the census areas.