Migrating

["Philip Veerman" <>]

The ABR in CBN in past years used to publish histograms of monthly abundance graphs, which would allow viewing of abundance trends of species during the subject year, thus meeting the role of an annual report concentrating on what happened during that year. This would be useful if it was reinstated, especially because now we have the ability to compare it to the long-term monthly abundance average graphs in the GBS Report (which came out after that information stopped coming out in the ABR). However in recent years the ABR have only been presenting the whole year as just one (ie single) more dot on a long-term graph. This does not allow useful viewing of comparative data, as to what happened during the year. There is also the serious problem that especially for winter migrants (such as Silvereyes), the two periods of peak abundance here (winter at the start of the year and autumn-winter at the end of the year) are combined into the one dot, making comparisons of abundance between two adjacent years almost useless. I have described the issue in the GBS Report. As for Yellow-faced Honeyeaters the trends for them are so much all over the place, due to observers and location differences, observers bending the rules in recording the numbers and no doubt also due to some real changes over the years, that picking any trend from GBS data, is more guesswork than anything else, beyond that the time of their migration is consistent.

 

Philip