Bermuda petrel
The Bermuda petrel is a gadfly petrel. Commonly known in Bermuda as the cahow, a name derived from its eerie cries, this nocturnal ground-nesting seabird is the national bird of Bermuda and is pictured on Bermudian currency. Bermuda petrels are the second rarest seabird on the planet. They have medium-sized bodies and long wings, a greyish-black crown and collar, dark grey upper-wings and tail, white upper-tail coverts and white under-wings edged with black, and the underparts are completely white.
For 300 years, it was thought to be extinct. The dramatic rediscovery in 1951 of eighteen nesting pairs made this a "Lazarus species", that is, a species found to be alive after having been considered extinct. Its rediscovery inspired a book and two documentary films. A national programme to preserve the bird and restore the species has helped increase its numbers, but scientists are still working to enlarge its nesting habitat on the restored Nonsuch Island.
Diet and foraging
Cahows typically eat small fish, squid and shrimp-like crustaceans. They also predominantly feed in colder waters. Geolocator studies carried out between 2009 and 2011 confirmed that they primarily forage in two widely separated locations during the non-breeding season, between Bermuda, Nova Scotia and North Carolina, and to the north and northwest of the Azores archipelago. Special glands in their tube-like nostrils allow them to ingest seawater. These glands filter out the salt and expel it through sneezing.Breeding
Historically, the petrels were superabundant throughout the archipelago, but because of habitat degradation and invasion of mammals, the bird's suitable nesting areas have dwindled to four islets in Castle Harbor, Bermuda, in the warm waters of the Gulf Stream, some 650 miles east of North Carolina. The cahow is a slow breeder, but excellent flier. It visits land only to nest and spends most its adult life on the open seas ranging from the North Atlantic coastal United States and Canada to waters off western Europe. After 3–4 years at sea, males return to breeding islands to create nests.Breeding season takes place during January and June. They nest in burrows and only the ones that can be in complete darkness are chosen. Females return after 4–6 years at open sea looking for a mate; the females lay one egg per season. 40% to 50% fail to hatch. Eggs are incubated by both parents and take 53–55 days to hatch. Hatching occurs between May and June. Cahows mate for life and typically return to the same nest each year.
In a first of its kind, a high school science project engaged in a remote study via live webcam using Cornell Lab's Cahowcam. It described incubation behavior of this species. The study found that sexes shared incubation duties equally; sedentary behaviors of incubating parent included resting, sleeping with head tucked back, preening, and nest maintenance ; nest attentiveness was high, with the egg left unattended only 1.5% of the observed time; and the incubating parent faced the nest entrance 49% of the time. Breathing rates and head shake movements were also measured for the first time in a seabird. Both parents were in the nest together for only 11 of the 55 days of observations. A parent was observed burying the inviable egg on the 68th day since laying.
History
The Spanish sailors of the 1500s used Bermuda and its surrounding islands as a waypoint to the Americas. At that time, cahows were abundant and formed dense, noisy colonies. These sailors, as Diego Ramirez wrote in 1603, would take up to 4,000 birds a night for food. In addition to eating birds, conquistadors brought hogs to the island to sustain themselves over their voyage. These hogs decimated the ground-nesting cahow, rooting up their burrows, eating eggs, chicks and adults and disrupting their breeding cycle.Following the Spanish visits to Bermuda, the English ship Sea Venture was wrecked on the island in 1609, and the survivors culled the fattest individual petrels and harvested their eggs in abundance, especially in January when other food were scarce. Although most of the survivors continued on to Jamestown in two newly built vessels, this shipwreck began the permanent settlement of Bermuda by the English as three men remained and were joined by others in 1612 when Bermuda was officially added to the territory of Virginia.
Bermuda's colonization by the English introduced species like rats, cats and dogs, and mass killings of the birds for food by these early colonists devastated their numbers. The remaining cahow population also decreased due to widespread burning of vegetation and deforestation by the settlers during the first 20 years of settlement. Despite being protected by one of the world's earliest conservation decrees, the governor's proclamation "against the spoyle and havocke of the Cohowes", the birds were thought to have become extinct by the 1620s.
Subsequent sightings of the cahow were believed to be confusion with the similar Sargasso shearwater. In 1935, William Beebe of the New York Zoological Society had hopes of rediscovering the bird. By June he was presented with an unidentified seabird that had struck the St. David's lighthouse in Bermuda. The bird was then sent to American ornithologist Robert Cushman Murphy of The American Museum of Natural history in New York. He identified the bird as a Bermuda petrel. Six years later, Bermudian naturalist Louis L. Mowbray received a live Bermuda petrel that had collided with a radio antenna tower. The bird was released after rehabilitation two days later.
After a bird that died flying into a lighthouse was identified as a cahow, on 28 January 1951, 18 surviving nesting pairs were found on rocky islets in Castle Harbour by Murphy and Mowbray and with them was a 15-year-old Bermudian boy, David B. Wingate, who would become the primary conservationist in the fight to save the bird.
Conservation
devoted his working life after that to saving the bird. After university studies and other work, in 1966 Wingate became Bermuda's first conservation officer. He undertook work to address various threats to the Bermuda petrel, including the eradication of introduced rats on the nesting islands and nearby islands, and addressed nest-site competition with the more aggressive, native white-tailed tropicbird Phaethon lepturus catsbyii, which invaded petrel nest burrows and killed up to 75% of all chicks. Following the design and installation of specially sized wooden "baffler" burrow entrance covers, which allowed the petrels to enter but excluded the larger tropicbirds, there has been essentially no further chick loss from this cause.Wingate also initiated the ecological restoration of Nonsuch Island, located near the Bermuda petrel breeding islets. Nonsuch was a near desert after centuries of abuse, neglect and habitat destruction. The measures that had to be taken weren't just for conserving what was left but also to recreate what had been lost, and thousands of endemic and native plants, including Bermuda cedar, Bermuda palmetto palm and Bermuda olivewood, were propagated and planted out on Nonsuch to recreate the original forest ecosystem that once covered Bermuda, but which was almost entirely lost through disease and clearing for agriculture, shipbuilding and residential development. In total, almost 10,000 individual native and endemic plants of over 100 species were planted on Nonsuch starting in 1962, and have since developed into a well-established closed-canopy forest, similar to early accounts of what was found on Bermuda by the earliest settlers in the 1600s. Wingate's goal was to restore the habitat on Nonsuch Island so that it could eventually serve as a viable nesting site for the species.
Even since his retirement in 2000, Wingate has designed and donated artificial plastic nest boxes to the Cahow Recovery Project, funded by the Bermuda Audubon Society. These nests were an effort made toward assisting the recovery of the Bermuda petrel, which normally nest in deep soil burrows or rock crevices but suffered from a shortage of suitable nest sites and soil for the birds to burrow in on the original nesting islets. Artificial concrete burrows have been used for many years to provide additional nesting opportunities for the birds, but are very labor-intensive to construct, requiring 400–800 lbs of concrete each. The new nest boxes were designed to meet the birds nesting needs, and it is hoped that they will assist in the recovery of the cahow for its future survival.
After Wingate retired, Jeremy Madeiros became the Bermuda Government terrestrial conservation officer, taking over the management of the Cahow Recovery Program and the Nonsuch Island Living Museum Project. Madeiros carried out a review of the status of the Bermuda petrel, identifying erosion of the four small original nesting islets due to hurricane damage and sea level rise as the single largest threat facing the species. A banding program for both fledgling and adult petrels was initiated in 2002, and by 2015 had resulted in over 85% of all Bermuda petrels being fitted with identification bands, enabling positive identification of individual birds through their breeding lifespan. Madeiros published a recovery plan for the Bermuda petrel, which provided guidelines and objectives for the management of the species, in 2005.