HomeNaturalist PostsBirdsFirst Cape May Warbler Ever Seen In the Lower Mainland


First Cape May Warbler Ever Seen In the Lower Mainland — 2 Comments

  1. The normal migration route in and out of northeastern BC is likely on a northwest-southeast axis east of the Rocky Mountains. The lower mainland bird appears to have exhibited a known migration navigation error called mirror-image migration. In this process, birds move in a flipped direction. So in this case, instead of migrating southeast as per normal in the fall, the bird moved southwest. If a bird normally migrates on a 40 degree SE direction from a centre line for example, the mirror image misorientation would send it on a 40 degree SW direction from the centre line.
    This type of navigation error is now thought of as being a consistent misorientation as opposed to a random disorientation. A certain percentage of a variety of species exhibit this anomaly, with the California coast being a consistent place where these breeders from northcentral and northeastern Canada arrive. Wind drift can assist this or even push them a little more off course. Some may remain on land, but some are felt to continue out to sea where they perish. The lower mainland bird appears to be remaining in a more hospitable place.

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