In the past, I’ve spent a lot of hours in Badgerow Park in Greece, counting fall warblers, for example, and mapping the territories of nesting birds.
It was a lot of fun, and I wouldn’t take back those hours for anything, but it did kind of warp my perspective on the abundance of certain species.
For example, Scarlet Tanagers do not nest in Badgerow because the woodlots are too small and fragmented.
I see them there only as spring and fall migrants, sometimes only one bird each season.
So my impression was that these brilliant songsters, which bring “a touch of the tropics” to our northern forests, were relatively scarce breeders in our region.
Until this summer.
When Cathy McCollumn and I spent a week visiting some of the best birding spots in our area, we heard the hoarse, burry, robin-like song and distinctive chip-burr call of Scarlet Tanagers in lots of places with large tracts of woodland.
They were abundant at Letchworth State Park and at Sterling Nature Center. We heard them along Norway Road, and at Beaver Lake Nature Center near Syracuse, and had a nice closeup look at one near Hemlock Lake Park.
This was all very encouraging, but there are still reasons to be concerned about the future of this colorful songster.
“As a species of the forest interior, it is sensitive to forest fragmentation, suffering high rates of predation and brood parasitism in small forest plots and often absent completely from plots less than a minimum size,” writes Thomas Mowbray in his profile of this species for The Birds of North America series.
For example, like the Wood Thrush and various other woodland species, Scarlet Tanagers are victims of Brown-headed Cowbirds, which lay their eggs in other birds’ nests and let the host parents incubate the eggs and raise the nestlings.
When this happens, the Scarlet Tanagers have much less success raising their own broods.
Cowbird parasitism is heaviest in areas where woodlots are relatively small and fragmented, giving the cowbirds, normally birds of open areas, easier access to the woodland species.
In fact, in the fragmented woodlots of largely rural central Illinois, rates of cowbird parasitism of tanager nests exceeds 80 percent, and these wooded areas are considered, in effect, “population sinks” that do not produce enough young Scarlet Tanagers to replace the adult population.
Project Tanager, conducted by Cornell Laboratory of Ornithology, found that in areas where the overall landscape was heavily forested, the minimum size of woodland patches needed by Scarlet Tanagers was less.
However, even when Scarlet Tanagers are found in small woodlots, that does not necessarily mean they will breed successfully. For example, in western New York, pairs could be found in patches of just about any woodland of more than 25 acres, “but fledgling success increased significantly with forest size,” note James Lowe and Ralph Hames in The Second Atlas of Breeding Birds in New York State.
As with many bird species, there are at least as many questions as answers when it comes to determining the best ways to protect Scarlet Tanagers.
“We need a better understanding of what constitutes quality habitat in various forest fragments,” Mowbray writes. Moreover, “almost no quantitative information is available regarding this species during migration or on its tropical wintering grounds.”
How sensitive is this species to fragmentation during migration and on those wintering grounds?
DID YOU KNOW
These are largely insect eaters, feeding on butterfly caterpillars and a variety of adult insects by hovering and gleaning them from leaves and bark, or sallying forth to catch flying insects in midair. When capturing bees and wasps, tanagers have been observed repeatedly beating prey against a branch or other hard surface until it is dead.
However, when insects are not plentiful, these birds will eat earthworms as well as wild and cultivated fruits, and even tender buds.
Both males and females sing. The female song is generally shorter, slightly softer and a little less harsh, Mowbray writes. “Female often sings together with male, immediately answering his song, while gathering nesting material and hunting; sometimes sings with nesting material or food in her beak.”
Scarlet Tanagers prefer to place their thin, loosely-woven, saucer-shaped nests in deciduous trees, among a cluster of leaves on a horizontal branch well out from the trunk, with a clear view of the ground and with clear, open flyways from adjacent trees, according to Mowbray.
The female builds the nest, incubates the clutch of four eggs, and broods the nestlings; however, the male helps with feeding the young and removing their fecal sacs.
What a stunning bird and NOPE, never saw one.
http://php.democratandchronicle.com/blog/birds/?p=3290
