Tuesday, August 23, 2011

Grassland birds of the Carden Plains IBA

Carden Plains Important Bird Area, near Kirkfield, Ontario (image courtesy of Bruce Wilson)

Nature Canada and Bird Studies Canada have been moving forward strongly on their Important Bird Areas program, working with local naturalist organizations and birders to conserve the ecosystems and monitor the birds on some of Canada's most critical pieces of avian habitat. Here in Saskatchewan and in other provinces, local naturalists are signing up to be volunteer caretakers for the IBA in their part of the country.

One IBA I hear a lot about is the Carden Plains in Ontario. Among naturalists in that province, there seems to be a fair bit of pride in the remnant populations of grassland birds at what many simply call the "Carden Alvar." What is an "alvar" was my first question. I hope to get to see the Carden Alvar some day, but while I was on Pelee Island this spring I visited a small alvar there and learned that it is a rare landscape on a base of limestone or dolostone that gives it a distinctive character and matrix of plant and animal species. Amazingly, Ontario is home to 75% of all North American alvars.

The Nature Conservancy of Canada (NCC) considers the Carden Alvar to be "an internationally significant natural area." Carden is even more imporant because it hosts rare and endangered species, including the Eastern Loggerhead Shrike and several declining species of grassland sparrows.

Bruce Wilson, a birder friend from Barrie, Ontario, recently agreed, after minimal arm-twisting, to write up a piece for Grass Notes explaining a bird banding project he has undertaken at Carden, along with his banding trainer, Nigel Shaw.

Bruce Wilson

Nigel Shaw

Their work caught my eye because they are taking advantage of the high number of birders who come to Carden by fitting banded birds with an additional plastic alpha-numeric band that can be read either in a spotting scope or digital photo. With this approach, any subsequent sightings of individuals will help Bruce and Nigel find out more about nest site fidelity, movement and distribution of the birds they band. Seems like a good idea to me, and it is always heartening to hear of people giving up their time and spending money out of pocket to gather data on our declining grassland birds.

I will let Bruce give you the full details on the project. Here is the report he graciously wrote up for me to post. (All bird photos by Nigel Shaw.)

The Carden Plain Important Bird Area near Kirkfield, Ontario, less than two hours northeast of Toronto, is southern Ontario’s premier area for grassland birds. It is a rare alvar habitat that supports a number of grassland birds including a breeding population of the endangered Eastern Loggerhead Shrike, as well as Bobolinks, Eastern Meadowlarks, Upland Sandpipers, Sedge Wrens, Eastern Bluebirds, Eastern Towhees, and Brown Thrashers. The typical grassland sparrows, Vesper, Savannah, Grasshopper and Field as well as Clay-colored also breed in the area as do Golden-winged Warblers.

The majority of land in the area is privately held with the exception of some areas that have come under the control of the Couchiching Conservancy. Major acquisitions are the Cameron Ranch, Windmill Ranch and Bluebird Ranch totalling some 5000 acres. These properties will eventually become an Ontario Provincial Park thus preserving portions of this unique area. The Couchiching Conservancy is also working with landowners in the area to encourage conservation of important habitats.

It is well-known that many species of grassland birds have declined rapidly over the past few decades. Once common species such as the Bobolink are now listed as threatened by COSEWIC. The decline of the grassland bird species is of concern.

Although some data are collected by means of annual point counts carried out on the Cameron and Windmill Ranches, typically in late May and early June, there are no data with respect to the ages of birds and the number of birds returning to nest each year. To obtain additional data Nigel Shaw licensed master bird bander from Alcona, Ontario and Bruce Wilson of Barrie, Ontario have undertaken a banding study with the permission of the Couchiching Conservancy and the Ontario Ministry of Natural resources. In particular they are focusing on several of the grassland species known to nest on The Ranches, namely: Upland Sandpiper; Clay-colored Sparrow; Savannah Sparrow; Vesper Sparrow; Grasshopper Sparrow; Bobolink; Eastern Meadowlark and Horned Lark.

Grasshopper Sparrow, just after banding

Banding studies have shown that many birds show a site fidelity and return to the same breeding area each year. The Carden IBA study will help determine if the same is true for the target species on The Ranches. The banding program will provide additional knowledge about movements of birds and will help determine the dynamics of the population trends of some of the typical grassland bird species by assessing the numbers of breeding birds and production of young. One advantage of carrying out a study on The Ranches is there are a large number of birders who frequent the area and will be able to report sightings of banded birds.

The study will be carried out over a number of years to collect the data necessary to better understand the breeding populations on The Ranches. The birds are attracted with audio lures and captured using conventional mist nests. When a bird is removed from the nets it is banded, wing chord measured made, weighed, moult patterns recorded, photographed and released. The birds are tagged with the standard bird bands as well as a plastic alpha-numeric band such that each bird will have a unique number. Studies of Green Finch in Europe using the same type of bands show the band numbers can be read with a spotting scope or by examination of digital photographs.

Adult Field Sparrow, showing alpha-numeric band

The program got off to a late start this years due to having to wait for delivery of the bands from overseas. On July 25 Nigel and Bruce went out to the Windmill Ranch hoping, given the late time, to be able to get a few birds but were pleasantly surprised with the results. In about 5 hours time they managed to band a total of 13 birds of which 10 were the target species. Although there were not many birds actively singing they responded well to the audio lures.

Clay Coloured Sparrow, just after banding

Target species banded:

Grasshopper Sparrow 2 adult, 1 hatch year
Clay Colored Sparrow 3 adult
Savannah Sparrow 1 adult, 1 hatch year
Vesper Sparrow 1 adult
Field Sparrow 1 adult

Other species

Yellow Warbler
Gray Catbird
Song Sparrow

An Upland Sandpiper responded to the call by coming into the net are but flying over. This bird was a different one than one heard a few minutes earlier.

Based on the results the birds will still respond to the audio lure despite the apparent lateness of the season. This bodes wells for work next year.

Next year's early efforts will focus on areas that lead to the various point counts on the Ranches hoping birds trapped there will be more likely to be seen again.

This is an interesting project and it is hoped it will give us more information about the little brown jobs most people do not give a second thought to.

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