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The highly gregarious Eared Grebe is best surveyed aerially (Cullen et al. 1999), but targeted aerial surveys do not exist for most breeding colonies. Thus, Canadian population trends must be inferred from continental data during staging and wintering. Christmas Bird Count (CBC) data suggest that the current North American abundance has shown a slight decrease but is similar to that measured around 1970, though with some strong fluctuations over the last four decades. However, these CBC results have low reliability because trends for Canadian breeders cannot be distinguished from the continent-wide trend, and because much of the population winters far offshore beyond the range of CBC coverage. Annual aerial surveys of birds at a major fall staging site on Mono Lake, California reveal a large decrease in numbers (see graph in table below). Though numbers have increased since 2008, they are still well below the level in 1996. Numbers at Great Salt Lake, Utah are similar to those in 1997 when the survey began. Overall, the current abundance of Eared Grebe is best assessed as having shown little change in Canada since 1970, but the reliability of this assessment is considered low.
Additional information on: Christmas Bird Count (CBC)
Additional information on: Number of Eared Grebe (+/- SE) on the surface of Mono Lake, California and Great Salt Lake, Utah, USA (no SE)
