Audubon Society to benefit from bluebird box workshop
Survival of the bluebird is the motivation behind a second bluebird box workshop this weekend.Aberfeldy Nurseries is partnering with Bermuda Audubon Society to raise awareness of the threat facing the bluebird, whose numbers are diminishing because of the threat by predators and the loss of critical habitat.As a result its survival is now totally dependent on man, according to the Bermuda Audubon Society.“Last year we partnered with the Bermuda Audubon Society for the first time and had a huge response,” said Julie Greaves of Aberfeldy Nurseries.“We must have done about 50 bluebird boxes on the day and a lot of people ordered them. Some people brought their children and it was a nice family project.”Aberfeldy is offering ready-made boxes as well as selling kits so that the boxes can be constructed at the nursery on Sunday between 1.30pm and 3pm.All proceeds will go to the Bermuda Audubon Society, whose president, Andrew Dobson, will be present to give a speech on bluebird protection.“Bluebirds are one of the few birds that you can actually open the box and monitor it,” said Ms Greaves. “It’s a great project, really easy to assemble. There is a nice bluebird population, but they used to live in the cavity of the cedar trees and there are not so many cedars around these days.”Location, height of the box from the ground and size of the entrance hole are all very important, so as to protect the birds from predators like rats, cats and other birds such as the starling, sparrow and kiskadee.“We need to give them that safe nesting place,” Ms Greaves stressed. “When you put them up you want to put them on a pole not right next to a tree because obviously the rats can climb up the tree and jump onto the box.“You need to locate them in a relatively open space. Some people actually grease the pole so the rat can’t get up the pole.”She added: “You can register your bluebird box online and send information back about the bluebirds which will start to nest in March.“That’s why we need to get them up and ready. I think it’s a worthwhile cause. You can buy the kits for $15 and the ready-made box for $25.”Mr Dobson said survival of the bluebirds is a major initiative for the Bermuda Audubon Society.“The population of bluebirds in Bermuda is estimated to be about 500, 600 birds.“One of the reasons for the formation of the Bermuda Audubon Society in 1954 was to help the bluebird and prevent it disappearing from Bermuda as a breeding bird. Bermuda is the only location outside eastern North America where it breeds.“However, it lost its main nesting habitat when nearly all of Bermuda’s cedar trees were wiped out by a cedar scale insect in the 1940s and 1950s.“Nest boxes were used successfully in the US and so a nest box programme was started in Bermuda. It has been hugely successful but boxes need to be monitored carefully as bluebirds are now totally dependent on artificial nest boxes.”Persons interested in making and maintaining a bluebird box are encouraged to go to www.audubon.bm and click on ‘Bluebirds’, where an information leaflet is available.
The Eastern Bluebird sialia sialia is native to Bermuda the only location outside North America where this species breeds.
Before man first settled in 1609, forest growth dominated the landscape. Bluebirds fed on coastal grasslands, nesting in old cedars and cliff cavities. There was an absence of non-avian predators.
In the last 50 years, the pressures put on the bluebirds to find suitable nest-sites have been immense:
l The house sparrow, passer domesticus, was introduced in 1870-74. Its numbers increased rapidly and began to displace bluebirds from natural cliff and tree cavities.
l In the late 1940s and 1950s, a scale insect caused the elimination of over 90 percent of the cedar trees in Bermuda.
l The European starling, sternus vulgaris, colonised in the 1950s and increased competition for nesting cavity species.
l House sparrows use bluebird nestboxes and are responsible for the slaughter of numerous bluebird chicks but starlings can be kept out by keeping an entrance hole measuring 1.5ins.
l The great kiskadee, pitangus sulphuratus, was introduced in 1956 to control the anolis lizard population but proved to have wide-ranging food preferences including young bluebirds.
l Pesticides such as DDT were widely used in Bermuda in the 1950s and 60s, especially on golf courses and gardens. Being an insectivorous species, one can only assume the bluebird must have suffered a decline.
l There has been a dramatic increase in the number of feral cats, especially since the introduction of cat feeding stations in the 1990s.
l The tropical fowl mite ornithonysus bursa, has caused a significant number of deaths in bluebird nestlings.
l Bermuda’s human population has increased threefold since 1900 to about 60,000. The resulting urbanisation means there are far fewer open spaces. Bluebirds disappear in favour of sparrows when housing densities reach two per acre, the mean housing density on Bermuda today.
l Vandalism has resulted in broken nestboxes and dead bluebirds.
However, great efforts have been made to halt the decline in bluebird numbers:
l A nest box scheme has been in place for many years. The campaign was initiated by the Bermuda Audubon Society in the 1950s.
l Workshops and publicity campaigns are regularly mounted.
l Efforts have been made to educate the public as to the plight of the bluebird and the part that individuals can play.
l Hundreds of bluebird nestboxes have been erected around Bermuda. The boxes keep out starlings but must be monitored constantly to keep out sparrows.
l Bluebird boxes have been erected in ‘trails’ on most of the Island’s golf courses.
l A small number of sparrow traps have been used to remove sparrows from bluebird nest-sites.
The population of bluebirds in Bermuda today is estimated to be between 500 and 600. The bluebird is now totally dependent on artificial nestboxes for breeding success and its survival in Bermuda can only be guaranteed with human help.
Source: Andrew Dobson, president of Bermuda Audubon Society
References: Bermuda Audubon Society Newsletters. Vol 9 No 2 (Summer ‘98), Vol 10 No 1 (Spring ‘99), Vol 10 No 3 (Fall ‘99).
