In this column, I will provide a synopsis of several scientific papers that recently appeared in ornithological journals.\u00a0 All of the papers deal with birds that occur regularly in Maine and some of the research was performed in our state.<\/p>\n
The practice of laying eggs in the nests of other species of birds is a hallmark of the Brown-headed Cowbird.\u00a0 This sneaky trick, called brood parasitism, poses a huge conservation threat to many species of eastern birds.\u00a0 These cowbirds have only been in the east for less than two centuries.\u00a0 Prior to the European colonization of North America, Brown-headed Cowbirds were found on the western plains, following bison to feed on the insects the bison displaced while grazing.<\/p>\n
With the conversion of eastern forests to pasture land, habitat was created that allowed cowbirds to spread east.\u00a0 The various species of birds that are hosts to the cowbirds\u2019 eggs and nestlings had no prior experience with cowbird brood parasitism and in many cases have not had time to adapt.<\/p>\n
M\u00e9lanie Guigueno and Spencer Sealy published a recent article in the Condor that examines the behavior of Yellow Warblers whose nests contain one or more Brown-headed Cowbird eggs.<\/p>\n
For species that are able to distinguish a cowbird egg from their own eggs, several behaviors are available to thwart the efforts of the cowbird to pawn off the rearing of her own young.\u00a0 Sometimes, a host grasps the cowbird egg in its bill and ejects the egg from the nests.\u00a0 This efficient method requires a fairly large bill (15 millimeters long). Unfortunately, the Yellow Warbler\u2019s bill is too short.\u00a0 Some hosts will puncture a cowbird egg, pick it up with its bill and eject the egg over the side of the nest.\u00a0 Yellow Warblers cannot do puncture-ejection of the eggs.<\/p>\n
However, Yellow Warblers do have a unique way of fighting back against cowbird brood parasitism.\u00a0\u00a0 They construct part of a new nest (embedded burial) or an entirely new one (true burial) over the parasitized clutch of eggs and start the egg-laying process over again.\u00a0 Sometimes, the pair of Yellow Warblers will simply desert a parasitized nest and seek a new nesting site.<\/p>\n
The authors studied 132 nests over 13 years. They found that burial of parasitized clutches occurred about two-thirds of the time and desertion was the strategy in the other cases.<\/p>\n
We are fortunate in Maine to have two breeding species of sparrows that frequent salt marshes: Nelson\u2019s Sparrow and Saltmarsh Sparrow.\u00a0 Both were formerly united as a single species, the Sharp-tailed Sparrow.\u00a0 Saltmarsh Sparrow has a more southerly distribution, breeding as far south as Virginia.\u00a0 Nelson\u2019s Sparrow along the Atlantic coast breeds from New Hampshire northward.\u00a0 In places like Scarborough Marsh, both species can be found in the same marsh, sometimes hybridizing.<\/p>\n
Chris Hill and colleagues recently published an article in the Auk on Saltmarsh Sparrows.\u00a0 This species has an unusual life history compared to other sparrows.\u00a0 Males do not maintain a territory and do not form pair bonds with females.\u00a0 The males are deadbeat dads; they do not participate in the rearing of the young.<\/p>\n
Using DNA comparisons, the researchers found that multiple partners were typical for female Saltmarsh Sparrows.\u00a0 Fifty-seven of 60 broods with at least two chicks resulted from females having two or more male partners.\u00a0 About a third of the broods had a different father for each chick.\u00a0 The most common result though was for one male to have fathered two or more but not all the chicks in a nest.<\/p>\n
The males moved around in the salt marsh, siring chicks in nests up to a mile apart.\u00a0 The life history of this species is really quite different from the strongly territorial reproduction of related species like Song Sparrows.<\/p>\n
A team of researchers including Maine ornithologists Tom Hodgman and Peter Vickery published a comparison of home range sizes and habitat use by Nelson\u2019s Sparrow and Saltmarsh Sparrows in the Wilson Journal of Ornithology.\u00a0 This work was done in Scarborough Marsh.<\/p>\n
The researchers used radio-transmitters to track the movements of 63 Nelson\u2019s and 77 Saltmarsh sparrows.\u00a0 Like the Saltmarsh Sparrow, Nelson\u2019s Sparrows do not defend a breeding territory.\u00a0 However, they do tend to spend most of their time in particular areas, overlapping with individuals of both species.\u00a0 Theses areas are called home ranges rather than territories.<\/p>\n
Using the location data from the radiotransmitters, the researchers found that the home range of male Nelson\u2019s Sparrows was over twice as large as that of male Saltmarsh Sparrows (a whopping 300 acres compared to a still impressive 125 acres).\u00a0 Females of both species had similar home ranges of 70 to 100 acres.<\/p>\n
[Originally published on July 4, 2010]<\/p>\n\n
In this column, I will provide a synopsis of several scientific papers that recently appeared in ornithological journals.\u00a0 All of the papers deal with birds that occur regularly in Maine and some of the research was performed in our state. The practice of laying eggs in the nests of other species of birds is a […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[424,433],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/302"}],"collection":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/users\/146"}],"replies":[{"embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/comments?post=302"}],"version-history":[{"count":2,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/302\/revisions"}],"predecessor-version":[{"id":304,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/302\/revisions\/304"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=302"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=302"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=302"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}