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Hunting tactics of Peregrines and other falcons - Section: 13 Page: 96 - Peregrine prey selection and eagle interference

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96

Huntin tactics of Pere ines

them in attacks on flocks of Dunlins. Frequently, both sexes pursued the same prey. However, if the male made the capture, he was chased and robbed by the female. I saw 14 males release and lose their catch. Some chases covered long distances with undetermined results. Probably to avoid piracy by conspecifics, male Peregrines, upon capturing a Dunlin, flew to forested headlands across the bay or carried their prey far inland. Others circled to a high altitude and consumed their prey on the wing. Peregrines, either male or female, also robbed four Merlins (Falco columbari us) of their just-caught prey.

Dunlins were hunted throughout the day; 46 kills were made prior to 12:00 and 48 after 12:00. The respective values for kills per hour of observation (1/8.1 and I/12.4) in morning or afternoon were not significantly different (G = 2.85, P >0.05). Peregrines often resumed hunting immediately after eating a Dunlin, which took 10 20 minutes.

Duck Hunts. The Peregrines rarely hunted ducks in the coastal study area. Only four kills were seen. A Green-winged Teal (Anas crecca) that was flushed and briefly pursued by an adult male was taken after it dropped into a shallow pool in the saltmarsh. The male carried his prey out of sight low over the vegetation. Female Peregrines pursued and captured three ducks larger than teal, presumably Northern Pintails (Anas acuta), which were seized on the tide flats after the ducks dodged the approaching falcon by plunging into shallow water.

Klepto-parasites. All three large ducks captured by Peregrines in the study area were forfeited without a struggle to Bald Eagles. On four occasions, duck- hunting Peregrines were followed by one or more Bald Eagles, which attempted to seize ducks that dodged the falcons by ditching into the water. Eagles also commonly joined and interfered with Peregrines that were hunting Dunlins. One or more eagles immediately started in pursuit of most falcons (50 60'/o) that had just caught Dunlins. The Peregrines usually managed to stay ahead, but three falcons, closely harassed by 2 4 eagles, released their Dunlin. Two of these falling prey items were retrieved in mid-air by eagles. In at least three cases, eagles pounced on Dunlins that had ditched into the water or dropped into grassy vegetation to dodge the falcon.

The following incident is a typical example of intra- and interspecific competition between falcons and eagles. In the afternoon of 16 January 2003, a male Peregrine stooped at a flock of Dunlins and pursued a single bird that split off and dodged repeated passes. The male was quickly joined by a female and four eagles, all of them alternately swooping at the Dunlin flying erratically 1 10 m high over the water. After a combined total of 10 12 passes, the Dunlin was caught by the female Peregrine, which was immediately set upon by the eagles. The falcon carried her prey far inland. Prey-carrying Peregrines were frequently but vainly chased by Glaucus-winged Gulls (Larus glaucescens). In addition, gulls often joined Peregrines that were pursuing lone Dunlins, and on two occasions gulls pounced on Dunlins that had ditched into the water to escape a swooping Peregrine.

OCR
Tag: duck ducks eagles falcon falcons flock flocks peregrine peregrines pintails

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