Raptors on three RNLAF airbases, Numbers, strikes, trapping and relocation.

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11th Joint meeting of Bird Strike Committee USA & Canada, Victoria BC, Canada 14-17 September 2009

Abstract

Since gulls, pigeons, starlings, waders and corvids are the dominant bird species on NW European airfields it is not surprising that habitat management systems are aimed at reducing the numbers of these species from the runway environment. In the RNLAF this is realized by a “poor grass” regime. This is based on the idea that by bottoming out the soil the available biomass will decrease and hence the number of birds foraging on this biomass. In practice this means that the grass is mown and the clippings are removed without applying any fertilization. Neither length nor species composition of the vegetation are focussing points, it is the decrease in soil productivity that counts. Fine tuning the regime is done by choosing the best time of mowing, early enough to prevent seed setting of those herbs that potentially attract birds and late enough to be able to confine to the minimum number of mowings. This regime is gradually introduced in the RNLAF; in the years 1985 to 1995 it was introduced on parts of the airbases while from 1995 onwards the full runway environment on all airbases was managed in this way. After a transition period of only a few years on most airbases it is possible to mow only once a year (Dekker &van de Zee 1996, Dekker 2000).

Opposition against the “poor grass” approach is often centred on the assumption that it would favour rodents and thus be contra productive against rodent dependent raptors. This paper uses 22 years of systematic bird counts on three F-16 airbases to assess the validity of this assumption.

Although raptors only constitute a minor part of the avifauna of an airfield they are well present in bird strike statistics. In the European Military bird strike database raptors take the 4th position (Dekker et al 2003). RNLAF statistics are used to demonstrate the nature of these raptor strikes and the relation with the presence of raptors on airfields. Trapping and relocation of raptors on one airbase is discussed and finally some implications from this study for bird strike prevention are given.