Aanvallende roofvogels en mensen

Over the years, reports of raptors attacking people have permeated the (local) newspapers in The Netherlands with some frequency. Most media-accounts have been credible in their presentation, and it is often the general public which suggests firm and unlawful action (read: killing). Very little has been published on the background of raptor attacks, the chances of encountering an aggressively defensive raptor and flight initiation distances of raptors. Also, few remedies have been suggested how to avoid being attacked. This paper intends to rectify this omission, and provides suggestions what data should be collected when attacking raptors can be observed. Accounts of raptors attacking people occur in Dutch newspapers with a frequency of between 0 and 5 times per year (which may not be a complete overview, though). The information provided is rarely detailed enough to extract biologically interesting data, except for the species involved and the seasonality of attacks: without exception Common Buzzards Buteo buteo, and the nestling stage of the breeding cycle (mostly when nestlings are at least 15 days old), respectively. In the mid-2000s, the number of breeding Buzzards in The Netherlands can be estimated at some 11,000 pairs. The maximum chance of encountering an aggressive Buzzard is then about 0.045%. Quantative information on aggressive raptor behaviour during nest visits (separately for egg stage and nestling stage) is available for five species nesting in the central and northern Netherlands in 1990-2008, i.e. for Honey Buzzard Pernis apivorus (60/233, respectively number of visits during egg and nestling stage). Goshawk Accipiter gentilis (260/693), Sparrowhawk A. nisus (158/279), Buzzard Buteo buteo (480/2069) and Hobby Falco subbuteo (12/39). Nest trees were repeatedly climbed to collect data on reproduction, sometimes even daily (introducing some pseudo-replication). During each visit, attacks (hits or feigned) were scored (data Rob Bijlsma). Similarly, attacks of Hen Harriers Circus cyaneus during the nestling stage were recorded on the Wadden Sea Islands of Ameland (2004. Olaf Klaassen) and Terschelling (2008, Peter de Boer). Of these species. Honey Buzzards never were recorded to attack (hitting nor feigning), whereas Hen Harriers were by far the most aggressive (11% of visits with direct hits, 39% with feigned attacks). Attacks during the egg stage were extremely rare, and were restricted to Goshawks (twice, i.e. 0.8% of the visits). During the nestling stage, only Goshawks and Sparrowhawks were recorded to hit the climber (resp. 11 and 7 times, concerning two and one individual(s) respectively. Feigned attacks were more frequent, but still accounted for only 0.6% of visits to nests of Buzzards, 2.5% of those to Sparrowhawk nests, 3.5% of those to Goshawk nests and 7.7% of those to Hobby nests (Table 1). All visits and all six species combined, only 21 hits were delivered during 4311 nest visits (0.5%). This frequency is about ten times higher than found for the general public, not surprising given the fact that the nests themselves were visited. Raptor attacks outside the breeding season are almost non-existent (one January report for Buzzard: Ardea 8 (1919), page 132). Flight initiation distances, as recorded whilst walking in woodland, heathland and farmland in western Drenthe in the northern Netherlands during August and September 2008, averaged 49 m in Honey Buzzards (n=6), 60 m in Hen Harrier (n=1), 72 m in Kestrel Falco tinnunculus (n=14), 75 m in Sparrowhawk (n=14), 94 m in Buzzard (n=26). 111 m in Goshawk (n=3), 119 m in Hobby (n=1), 208 m in Peregrine Falco peregrinus (n=3) and 217 m in Osprey Pandion haliaetus (n=1). Six remedies are suggested to cope with aggressive raptors (except for raptorphiles, who deserve being attacked): 1. Do realise that the problem is temporary, involving a breeding bird (usually the female) with nestlings. Nestlings are brooded more or less full-time up to an age of two weeks old. From then on, the female spends more time in the vicinity of the nest, and is more prone to aggressively defend her chicks. The defensive period hardly ever extends beyond a duration of 2-3 weeks (in May and/or June), and attacks cease altogether as soon as the nestlings have fledged. 2. Do not create a bigger problem by exaggerating raptor attacks. Attacks by raptors are exceedingly rare (in The Netherlands); real hits are even more so. Most attacks are feigned, and often from behind. The only raptor species known to sometimes aggressively defend her nest, and breeding in the vicinity of the human population, is the Buzzard (the highly aggressive Hen Harrier is rare and breeds away from human populations). Blows with the talons are often targeted at the head, which may result in lacerations, bruises or punctures. 3. When an aggressive raptor is located, avoid the immediate surroundings of the nest (<100 m) for the duration of the breeding cycle. In The Netherlands, where the network of paths and roads is dense, a detour can easily eliminate the risk of being attacked. 4. Do be alert when entering the home range of an aggressive raptor, actively look around to timely notice an attack (or attempt thereof), and face the raptor (rather than face away, which is a stimulus to start an attack). Putting up warning signs may promote a more alert attitude of the public. 5. Most attacks can easily be thwarted by shouting and vigorously waving with hands and arms. 6. Increasing flock size often suffices to prevent attacks. Even two people run already a smaller risk of coming under attack than when alone.