Birds:  staple of the diet
Most peregrines feed almost exclusively on birds, and in many parts of the world pigeons and doves are their favourite prey. However, peregrines actually hunt a wide variety of birds. At the Toronto and Etobicoke nests, 17 species of prey have been identified to date, including such surprises as American woodcock, Baltimore oriole, and eastern meadowlark. This list pales in comparison though to the 47 species which Regina’s peregrines have dined on over the past decade.

In wild settings, the peregrine’s diet is even more diverse. A six-year study in southern Scotland recorded more than 3500 prey of 74 species. Nearly half of the individuals were rock doves (i.e. pigeons), and overall the 15 most common species comprised 91% of all prey. However, the range of prey was remarkable - birds as small as the 6-gram goldcrest were taken, as well as male black grouse weighing almost 1.2 kg! An even wider variety of species have been documented as prey in California, where the list of birds hunted by peregrines now exceeds 160 species, from as small as the yellow warbler and red-breasted nuthatch to quite large birds such as western grebe, pelagic cormorant, and black-crowned night heron.

The classic hunting method of the peregrine is the high speed stoop in which it kills prey by striking it in mid-air. Clearly this technique is not always suitable. With large prey such as a goose or pheasant, a peregrine may grab hold and ride the larger bird to the ground. This sometimes involves the two birds tumbling through the air together in seemingly reckless fashion. In coastal areas, peregrines have been seen chasing land birds offshore to tire them out, and on occasion even plucking them from the surface if they drop into the water.

Insects:  snacks just for fledglings
For a bird the size of a peregrine, insects don’t make much of a meal. However, fledglings are often observed testing their hunting skills on large insects such as dragonflies and butterflies; perfect practice for the skills needed to catch aerobatic birds.

Mammals:  popular at climatic extremes
In temperate regions, peregrines kill the occasional vole, squirrel, or rabbit, but mammals rarely exceed 1% of their prey. The situation is quite different in the arctic, where lemmings and ground squirrels are hunted regularly and may account for as much as half of the diet Interestingly, at least some tropical populations rely heavily on mammals too. In Fiji, a study of the peregrines nesting within the rain forest fed predominantly on flying fox fruit bats. In North America, juvenile peregrines have been seen hunting migrating bats on occasion.

Fish, amphibians, and reptiles:  a balanced diet?
Though peregrines aren’t adapted for fishing, the occasional individual has tried it all the same. Reports exist in the literature of a brown trout in a Scottish peregrine nest, and a salmonid fish being delivered to an Idaho eyrie by an adult. Some observers have been fortunate enough to see peregrines capturing fish from rivers, or in one case even from the sea off Tasmania! Surprisingly, the occasional amphibian or reptile graces the peregrine’s menu too. A study in Spain found one lizard and an unidentifiable frog among prey remains, and in Fiji a large gecko was discovered at a nest. Thus, while we may think of peregrines being primarily bird-hunters, the reality is that they are opportunists who can adapt their hunting techniques according to the prey which is available.

References: (supplemented by observations from CPF records)
Barnes & Garwood. 1995. Peregrine falcon takes a fish in Idaho. Journal of Raptor Research 29: 283-284.
Bradley & Oliphant. 1991. The diet of peregrine falcons in Rankin Inlet, NWT: an unusually high proportion of mammalian prey. Condor 93: 193-197.
Byre. 1990. A group of young peregrine falcons prey on migrating bats. Wilson Bulletin 102: 728-730.
George. 1979. Snow goose taken by peregrine falcon. Raptor Research 13: 88-90.
Heredia et al. 1988. Status, ecology, and conservation of the peregrine falcon in Spain. In: Cade et al (eds): Peregrine falcon populations: their management and recovery, pp. 219-226. Boise, Idaho: The Peregrine Fund.
Horne & Short. 1989. Peregrine falcon takes black-bellied plover from sea off Kenya. Journal of Raptor Research 23: 181-182.
Mearns. 1983. The diet of the peregrine in south Scotland during the breeding season. Bird Study 30: 81-90.
Parker. 1978. Peregrine quartering ground like harrier. British Birds 71: 37.
Santa Cruz Predatory Bird Research Group. 2001. Peregrine prey items. www.angelfire.com/ca2/peregrinefalcon/prey.html.
Triffo. 2000. The hunting behavior and prey selection of urbanized peregrine falcons. http://falcon.unibase.com/triffo/preylst6.htm.  
Weir. 1979. Brown trout among food remains in a peregrine’s nest. Bird Study 26: 200.
Wendt et al. 1991. Juvenile urban-hacked peregrine falcons hunt at night. Journal of Raptor Research 25: 94-95.
White et al. 1988. A study of peregrines in the Fiji Islands, South Pacific Ocean. In: Cade et al (eds): Peregrine falcon populations: their management and recovery, pp. 275-287. Boise, Idaho: The Peregrine Fund.