Sunday, December 5, 2010

Baby Boobies

The Masked (Tasman) boobies are having an extended breeding season in the island's north, as usual. At Nepean Island if the chicks are to be banded they need to be caught before they are flying, by about August/September. Phillip Island chicks, only 5-6 kilometres away to the south, are still unfledged by January. An unexplained difference of many months for the same species separated by just a short stretch of water. It would be interesting to track where their feeding grounds are to find out if the two groups go to distinct and separate areas, where the food availability may be different.

The Tasman Booby differs from other Masked Boobies, in being larger and having brown eyes. It was thought to have been an extinct species when fossilised bones were unearthed in the 1960s, but recent work utilising DNA sequencing has shown that the brown-eyed birds are the same as the 'extinct' Tasman booby. This brown-eyed group are found only in Norfolk, Lord Howe and the Kermadec islands, (north-east of New Zealand at about the same latitude as Norfolk).

Chicks are at that awkward teeenage stage now on Norfolk. A few still look like Sesame Street's Big Bird but many have preened and waved their wings about enough that their first flight feathers are coming through and only patches of down remain.

The juvenile plumage is mottled brown and these birds are often mistaken for 'another' species.

The boobies in these photos are part of the same group whose images appeared in the article in Australian Geographic in January 2010. Along with other seabird species that nest on the ground, these birds are breeding regularly on private property, where they are not disturbed. Ground-nesting seabird species have been all but obliterated from Norfolk's main island where feral cats, domestic cats and dogs, and rats kill them or drive them away. Humans have played their part in pushing these charismatic boobies off Norfolk Island in the past by disturbing them at their breeding grounds in the mistaken belief that the birds didn't mind the intrusions of people who had to get up close and personal for their photographs or just because they could. The parent birds seem unconcerned but are staunchly protecting their eggs or small chicks, and often when people have departed the stress of their presence will cause the parent birds to regurgitate the hard-won fish they have been diving for at sea to feed their chicks. The chicks don't leave because they can't fly, and cannot escape even if they wanted to.
 The birds in these photographs are given protection through constant trapping of feral cats and rat baiting in the area. Dogs are not allowed on the property unless restrained and people are kept at a distance or under close supervision.
We believe that all species are constantly looking for areas into which they can extend their territory and the only things stopping them all over Norfolk are predation and interference.
It may be that the increasing number of boobies now breeding at the northern coast of Norfolk and on the offshore rocky stacks (seen across from Cooks Monument and the Bridle Track) are moving from Phillip  Island where greater visitation is disturbing them in recent years. It may also be that as their numbers increase they simply need to find more areas to occupy.

1 comment:

  1. Love the baby booby pics, Marg. Do you have any idea of how booby numbers are heading - up or down? Linda E