Maine

The Rusty Blackbird Spring Migration Blitz is an effort to map the locations and numbers of Rusty Blackbirds during spring migration over the next three years. The Blitz encourages you to bird for conservation. You will support an initiative to identify conservation challenges and develop strategies to conserve a vulnerable songbird!

Please help make the survey in Maine a success. Here we discuss:

• Spring Blitz
• Why the Blitz?
• Historical status
• Identification tips

 

Spring Blitz

The request is simple: go out and look for birds, then record what you see by entering your data into eBird using the special Rusty Blackbird data entry protocol.

When

Maine’s target for surveys is mid-March through April. The Rusty Blackbird is quick to return to its boreal forest breeding grounds in spring, arriving before the snow has gone from the ground. Wintering in the Southeast, they are rarely reported in Louisiana, for example, after the first week of April. Even as close to the breeding range as  New York City they are rarely found after early May, by which time most are on the breeding grounds. Although a few winter in Maine, typical arrival dates here are mid-late March, with widespread arrival around that time. They peak in numbers through mid-April.

Where

Wooded swamps are prime habitats for Rusty Blackbirds, but they might stop in cornfields, pastures, and many other locations on migration. Rusty Blackbirds like to get their feet wet while foraging, favoring areas with shallow, still water. They are often found lurking low in wet wooded and shrub swamps.

So that’s your job. Find them. Once each of your field searches for Rusty Blackbirds is finished, the data are to be entered into eBird.

Equally important, even if no Rusty Blackbirds are found, a report should be submitted. You may also simultaneously enter the complete list of all the birds including numbers encountered during your search (and keep on eBirding after the Blitz!). It is important to search widely and submit your data whether or not you detect Rusty Blackbirds.

 

Why the Blitz?

One hundred years ago the last Passenger Pigeon died at the Cincinnati Zoo. One hundred years before that Alexander Wilson estimated the size of a flock flying between Kentucky and Indiana at 2.2 billion birds. The 1870s and 1880s was a period of precipitous decline for the pigeon, with the number of nesting birds going from millions to thousands. Some realized by then that the Passenger Pigeon needed help, but it was too late. Within fifty years they were gone forever.

• How is it possible that such a common bird could spiral into extinction?
• How do we recognize such a downward spiral while it is happening?
• What can we do if we see it happening today?

Over the past 50 years, the Rusty Blackbird has declined more significantly than any other North American landbird (Greenberg et al. 2011). Although still fairly numerous, this trend demands attention. Hence the International Rusty Blackbird Working Group has initiated  programs aimed at learning more about the life history of this once abundant bird.

 

Historical Status

Here in New England at the eastern edge of the species range, the huge numbers that passed north in the middle of the continent were never seen. Nevertheless, the species was fairly common and more numerous than today. It is still an anticipated part of spring migration here. To our west from the Great Lakes to the prairie provinces where the bulk of Rusty Blackbirds pass north, they were abundant. To give a hint of their former status, read what Ernest E. Thompson wrote about the spring migration through Manitoba in the late 1800s.

“They blacken the fields and cloud the air. The bare trees on which they alight are foliated by them. Their incessant jingling songs drown the music of the Meadow Larks and produce a dreamy, far-away effect, as of myriads of distant sleigh bells.” (Birds of Manitoba 1891)

What is the evidence for decline?

Based on standardized Breeding Bird Survey (BBS) census data, Rusty Blackbirds declined range-wide more than 95% from 1966 to 2005. Even though BBS routes are not sampling the whole boreal forest breeding range, a similar magnitude of decline is seen in winter population censuses. Analyses of Christmas Bird Counts reveal a decline of 85% over the same 40 year period.

The breeding range has retreated from its former southern limits as well. In Maine the Rusty Blackbird’s breeding range has contracted 65-160 km over the last century, with the most marked change occurring since the 1970s and 1980s (Powell 2008, also see more recent papers here). As a consequence, Maine’s department of Inland Fisheries and Wildlife has placed the Rusty Blackbird on its lists a Species of Special Concern.

—Map of Rusty Blackbird range contraction in Maine (from Powell 2008). Extent of range in 1908 includes all colored regions south to light green area (Knight 1908), as of 1949 south to olive and brown areas (Palmer 1949), as of 1978–1983 blue and brown areas (Adamus 1987), and as of 2007 blue area only (Maine Ecoregional Surveys: Hodgman and Hermann 2003, Hodgman and Yates 2007; survey work by Powell 2008).

Why are they declining?

Several factors may underlie the decline and contribute in concert. The leading causes under study include:

• winter habitat loss in the Southeast where bottomland hardwood forests have largely been converted to agriculture and had their hydrology altered.
• loss and degradation of boreal breeding habitat, e.g. through desiccation and fragmentation. Rusty Blackbirds forage in shallow wetlands and perhaps especially depend on widely scattered temporary pools and puddles where they prey on aquatics such as snails and larvae of dragonflies, damselflies, and caddisflies. A natural disturbance combined with subsequent human changes that occurred around the beginning of the Rusty Blackbird’s decline was the outbreak of spruce budworm (Choristoneura fumiferana) from 1968 to 1985, an event that defoliated 55 million acres from Lake Superior east to the Atlantic coast and that was subsequently salvage-harvested causing widespread changes to breeding habitats.
• blackbird control efforts on the wintering grounds, e.g. depredation of blackbird flocks as crop pests in the South.
• migratory Allee effects, a situation where birth rate declines at low population densities because of the increased difficulty of finding a mate. The Rusty Blackbird nests across a vast landscape and in widely dispersed pairs, rarely loose colonies. Such a life history is more prone to a downward spiral from Allee effects.

 

Identification

If you need to brush up on how to identify Rusty Blackbirds, download this handy brochure with photographs and pointers. Another good resource for identification help is the NatureInstruct website Dendroica, offering photos, sounds, and maps.

Vocalizations

William Brewster described the spring arrival and vocalizations of the Rusty Blackbird in New England:

“The Rusty Blackbird comes to us from the south in early spring about the time when Pickering’s hyla begins peeping. The tinkling notes of the Blackbird are, indeed, ever associated in my mind with the bell-like call of the hyla, for at this season the two sounds are usually heard together. Being pitched on nearly the same key, it is not always easy to discriminate them, especially when a score of Blackbirds and several hundred hylas are exercising their vocal organs at once.” (The Birds of the Cambridge Region of Massachusetts, 1906)