We are all accustomed to misleading or even paradoxical phrases in our conversations that we often use without thinking.\u00a0 Shouldn\u2019t a \u201cnear miss\u201d be a glancing collision?\u00a0 Have you ever gotten a \u201cfree gift\u201d?\u00a0 Biology is not immune from such phrases and \u201cfall bird migration\u201d is at the top of my list.<\/p>\n
Even though none of use wants to admit that the days are growing shorter, we are still in summer.\u00a0 Nonetheless, migration of birds is well underway.\u00a0 The southward movement will continue through autumn and into early winter.\u00a0 \u201cFall migration\u201d is misleading; I prefer \u201cpost-breeding migration\u201d.\u00a0 The majority of our swallows depart by the end of August and therefore never spend an autumn day in Maine.<\/p>\n
Shorebirds (particularly sandpipers and plovers) are now migrating through Maine from their more northerly breeding grounds en route to more southerly wintering grounds.\u00a0 Shorebirds are some of our earliest and most remarkable migrants.<\/p>\n
The majority of shorebirds that pass through Maine during migration breed at high latitudes on the Arctic tundra.\u00a0 For about six weeks (June to the middle of July), the arctic tundra is great habitat for sandpipers and plovers.\u00a0 Insect life is abundant and the sun never sets.<\/p>\n
We describe the reproduction of shorebirds as precocial.\u00a0 The chicks hatch fully feathered, a striking contrast to the altricial development of most songbirds whose young hatch as naked, blind chicks.\u00a0 Within hours of hatching, young shorebirds are walking around, catching their first insect meals.\u00a0 The shorebird parents (sometimes only the mother in some species like the Buff-breasted Sandpiper and sometimes only the father in Red-necked Phalaropes and Red Phalaropes) guard the young but do not typically feed the young.\u00a0 The young do have cryptic coloration, blending into the tundra to avoid the eyes of predators like Arctic foxes and Snowy Owls.<\/p>\n
The short breeding season in the arctic means that parents only have time for one brood per season.\u00a0 To increase the chances of surviving another year and reproducing again, sandpipers are under pressure to begin their southbound migration as soon as possible.<\/p>\n
Because the nestlings can fend for themselves, the parents usually migrate from the breeding grounds before their young have even learned to fly!\u00a0 As a result, southbound shorebird migration occurs in two pulses.\u00a0 Along the Maine coast, the first adult shorebird migrants begin showing up by the middle of July.\u00a0 The first juveniles show up later; juvenile sandpipers and plovers will arrive mostly in August and September.\u00a0 In some species like the Semipalmated Sandpiper, the adult females leave the breeding grounds before the adult males producing a three-step migratory wave along the migration route: adult females, adult males and then juveniles.<\/p>\n
After the parents have departed, the juvenile shorebirds learn to fly on their own and depart for wintering grounds they have never seen.\u00a0 With no adults to guide them, the juveniles must have the migratory route somehow encoded in their brains.\u00a0 We know that juvenile navigation is not as accurate as that of adults.\u00a0 During the southbound migration, shorebirds that occur as rarities are usually juveniles.<\/p>\n
By ageing shorebirds, birders can increase their enjoyment and appreciation of the southbound migration.\u00a0 How does one go about determining if a shorebird is a juvenile or adult?\u00a0 Some adult migrants still have some of their breeding plumage.\u00a0 So a Black-bellied Plover or Dunlin with a black belly during southbound migration has to be an adult.\u00a0 However, adults often molt into their winter plumage along the migratory route and may resemble juveniles.\u00a0 A look at the wear of the feathers can usually allow one to distinguish such adults from juveniles.\u00a0 As a general rule, juveniles have brighter and crisper plumages.\u00a0 The feathers of the juvenile are only a few weeks old and the adult feathers are a couple of months older and hence more worn.<\/p>\n
[First published on August 5, 2012]<\/p>\n\n
We are all accustomed to misleading or even paradoxical phrases in our conversations that we often use without thinking.\u00a0 Shouldn\u2019t a \u201cnear miss\u201d be a glancing collision?\u00a0 Have you ever gotten a \u201cfree gift\u201d?\u00a0 Biology is not immune from such phrases and \u201cfall bird migration\u201d is at the top of my list. Even though none […]<\/p>\n","protected":false},"author":146,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"yes","ngg_post_thumbnail":0,"footnotes":""},"categories":[429],"tags":[],"builder_content":"","_links":{"self":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/520"}],"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=520"}],"version-history":[{"count":2,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/520\/revisions"}],"predecessor-version":[{"id":522,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/posts\/520\/revisions\/522"}],"wp:attachment":[{"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/media?parent=520"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/categories?post=520"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/web.colby.edu\/mainebirds\/wp-json\/wp\/v2\/tags?post=520"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}