Probing at the soft substrate along mudflats and sandbars, the American oystercatcher feeds mainly on oysters, mussels, clams and limpets, as well as snails and crabs (2). Once its shelled prey is found, this large-billed bird goes about opening it up using two main methods. If its prey is taken by surprise and its shell is already open, the American oystercatcher quickly drives its bill between the shell halves, severing the adductor muscle (the muscle that holds the shell halves together) with a scissor-like movement and the flesh is chiselled out. If the shell is closed, repeated blows of the beak are used to prise the shell apart and the flesh is removed (8) (6). There is great variation between individual birds as to what prey is principally eaten and what techniques are used. Young oystercatchers rely heavily on the parents to learn these techniques, but for their first year of life they feed largely on scraps left by adults as the bill and skull is not sufficiently strong to open shells until their second year (6).
Outside of the breeding season, the American oystercatcher is highly gregarious, gathering into large flocks when foraging, roosting and migrating (4). However, during the breeding season, which takes place between February and July, monogamous pairs collect at specific breeding sites, with the female arriving up to three weeks before the male (3) (8). Once paired up, a simple nest, which is no more than a scrape in the ground, is constructed in an elevated position just above the high water mark (2) (3). During this time, the breeding pair is highly territorial and will fiercely defend an area around the nest, which may vary from just a few metres away, to a kilometre stretch of the beach (4) (7). To mark their territory, birds engage in ‘piping displays’ whereby the adult bird stands with its neck arched and bill pointed downwards, all the while emitting a series of piping notes (6). A clutch of 1 to 4 eggs is laid and subsequently incubated for 24 to 29 days by both the male and female (2) (3). To disguise the eggs, pieces of broken shell or pebbles are placed inside the nest, and to distract potential predators, the parents will feign injury away from the nest or even pretend to brood a clutch away from the actual eggs (3). Within 24 hours of hatching, the chicks are capable of running and leave the nest only 1 or 2 days later (3) (7). They learn to fly within five weeks, but due to the American oystercatcher’s specialised diet, the young continue to accompany the parents to learn the basic feeding techniques and it is several months before they become fully independent (2) (4). The American oystercatcher reaches sexual maturity after a year, and regularly lives to reach over 10 years of age, with some individuals perhaps living as long as 30 or even 40 years (3) (4).