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--Boundary_(ID_mgJDxYC7uvVnXlvkjSQA6w) Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7BIT Paul Boyer wrote: > I wonder sometimes if all the feeders around may be confusing some of these > birds who ought to be migrating. Availability of food is the main motivator for > small birds, and even for some of the larger ones. I have read that most > Canada Geese no longer bother to migrate: they find so many nice lawns of grass > that can sustain them, that it is more profitable for them to just avoid all the business > of long-distance flying, which is exhausting and dangerous. Hi Paul, For those long distance migrants that breed in Nova Scotia, the availability of food is not the main motivator for migrating. Day length is the factor which triggers fall migration. Most species of warblers etc. leave in August and September when food is still widely distributed and amply available. A lack of food will drive birds out of an area but that is regardless of the season. Most people with bird feeders annually observe individuals and groups of some species showing up at their feeders, staying for a short period and then disappearing until the following spring arrival in spite of the fact that there is plenty of food at their feeders. Another observation from NatureNS that is illustrative is that this fall some people reported how few birds they had at their feeders and it was only in the late fall/early winter when birds moved to them. Both of these examples support the idea that bird feeders do not keep migratory species at a feeder instead of heading south. There are a few factors which confound observing this 'normal', migratory behaviour. First, there is individual variation and condition so every winter there will be some reports of unexpected species showing up at feeders. Birds may be in poor condition due to local conditions or due to sickness and are in no shape to migrate. The vast majority of these birds would die without supplemental human feeding and, in fact, most do die in spite of the fact that they find feeders. Individual variation results in some birds, regardless of their physical condition, sticking around. Again, most of these individuals perish during Nova Scotia's winters. However, some survive, with and without bird feeding. This type of individual variation is what may allow a species to take advantage of changing environmental conditions. Second, there are different species-wide strategies. As was discussed earlier on this list, Blue Jays for example, exhibit multiple strategies, with large numbers leaving Nova Scotia in the fall, other groups heading south but staying in the province and others not moving far at all. As with individual variation, this probably allows them to exploit changing environmental conditions and increases the species' chances of survival by not exposing the entire population to the same conditions (sounds like a financial advisor's advice to diversify an RRSP). Third, there are weather events that trap birds in Nova Scotia. Again, it is probably rare that these birds manage to successfully head back south after this. Some however, may survive through human intervention. Paul, as you point out in the Canada Goose situation, there are many species which have adopted new strategies because of human activities. However this isn't confined to bird feeding. A number of Nova Scotia breeders are non-native to North America and exist in the province only because of direct human introduction. Many others breed in habitat such as farmland that only exists because of humans. Still others (e.g. Herring and Great Black-backed Gulls) have their survival enhanced by human activities other than backyard bird feeding. Lastly, there is no question that a number of species take advantage of bird feeders. In fact, there are a number of species which have probably taken advantage of bird feeding to expand their ranges north into the province (e.g. Mourning Dove, House Finch, Northern Cardinal). However, these species are either short distance migrants or year round residents even in those areas where there are no bird feeders. All the best, Lance --Boundary_(ID_mgJDxYC7uvVnXlvkjSQA6w) Content-type: text/html; charset=us-ascii Content-transfer-encoding: 7BIT <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content="text/html; charset=us-ascii" http-equiv=Content-Type> <META name=GENERATOR content="MSHTML 8.00.6001.18876"></HEAD> <BODY style="WORD-WRAP: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space"> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>Paul Boyer wrote:</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>> </FONT></SPAN>I wonder sometimes if all the feeders around may be confusing some of these <SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial> </FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>> </FONT> </SPAN>birds who ought to be migrating. Availability of food is the main motivator for <SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial> </FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>> </FONT> </SPAN>small birds, and even for some of the larger ones. I have read that most <SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial> </FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>></FONT> </SPAN>Canada Geese no longer bother to migrate: they find so many nice lawns of grass <SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial> </FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>></FONT> </SPAN>that can sustain them, that it is more profitable for them to just avoid all the business <SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial> </FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>> </FONT> </SPAN>of long-distance flying, which is exhausting and dangerous.<SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial> </FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>Hi Paul,</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>For those long distance migrants that breed in Nova Scotia, the availability of food is not the main motivator for migrating. Day length is the factor which triggers fall migration. Most species of warblers etc. leave in August and September when food is still widely distributed and amply available. A lack of food will drive birds out of an area but that is regardless of the season.</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>Most people with bird feeders annually observe individuals and groups of some species showing up at their feeders, staying for a short period and then disappearing until the following spring arrival in spite of the fact that there is plenty of food at their feeders. Another observation from NatureNS that is illustrative is that this fall some people reported how few birds they had at their feeders and it was only in the late fall/early winter when birds moved to them. Both of these examples support the idea that bird feeders do not keep migratory species at a feeder instead of heading south.</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>There are a few factors which confound observing this 'normal', migratory behaviour. First, there is individual variation and condition so every winter there will be some reports of unexpected species showing up at feeders. Birds may be in poor condition due to local conditions or due to sickness and are in no shape to migrate. The vast majority of these birds would die without supplemental human feeding and, in fact, most do die in spite of the fact that they find feeders. Individual variation results in some birds, regardless of their physical condition, sticking around. Again, most of these individuals perish during Nova Scotia's winters. However, some survive, with and without bird feeding. This type of individual variation is what may allow a species to take advantage of changing environmental conditions.</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>Second, there are different species-wide strategies. As was discussed earlier on this list, Blue Jays for example, exhibit multiple strategies, with large numbers leaving Nova Scotia in the fall, other groups heading south but staying in the province and others not moving far at all. As with individual variation, this probably allows them to exploit changing environmental conditions and increases the species' chances of survival by not exposing the entire population to the same conditions (sounds like a financial advisor's advice to diversify an RRSP).</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>Third, there are weather events that trap birds in Nova Scotia. Again, it is probably rare that these birds manage to successfully head back south after this. Some however, may survive through human intervention.</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>Paul, as you point out in the Canada Goose situation, there are many species which have adopted new strategies because of human activities. However this isn't confined to bird feeding. A number of Nova Scotia breeders are non-native to North America and exist in the province only because of direct human introduction. Many others breed in habitat such as farmland that only exists because of humans. Still others (e.g. Herring and Great Black-backed Gulls) have their survival enhanced by human activities other than backyard bird feeding. </FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>Lastly, there is no question that a number of species take advantage of bird feeders. In fact, there are a number of species which have probably taken advantage of bird feeding to expand their ranges north into the province (e.g. Mourning Dove, House Finch, Northern Cardinal). However, these species are either short distance migrants or year round residents even in those areas where there are no bird feeders.</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>All the best,</FONT></SPAN></DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial></FONT></SPAN> </DIV> <DIV dir=ltr align=left><SPAN class=084204713-01022010><FONT color=#0000ff size=2 face=Arial>Lance</FONT></SPAN></DIV></BODY></HTML> --Boundary_(ID_mgJDxYC7uvVnXlvkjSQA6w)--
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