It was a strange Fall banding season, a boom or bust situation for two of our main species: Cedar Waxwings and American Goldfinches.
The Cedar Waxwing numbers could only be described as spectacular – we banded 1,481, well more than two standard deviations above the 14-year average of 129 and 819 above our previous high count (662 in 2011).
There has been an interesting increase in Cedar Waxwing numbers at Ruthven since we began Fall banding in earnest in 1996. This increase is entwined in the arrival of wild grapes (Vitis riparia) to the site which began slowly in the initial years but jumped dramatically in 2010, as did bird numbers; in fact, you could almost say that you could date the arrival of wild grapes to the site with the increase in waxwing numbers. From 1996 to 2009 we averaged only 45.8 waxwings banded each Fall. (Interestingly, we banded only 2 in 2009!) But then the floodgates opened: 422 in 2010; 662 in 2011; 196 in 2012. These numbers are related to the presence of Wild Grapes – in 2012 there were none due to weather anomalies in the Spring and there was a drop-off….but only when compared to the two previous years. But this year we had a bumper crop of grapes and waxwings were around in huge numbers starting in September and building through October/November. (We banded 196 in September, 1,123 in October, and 162 in the first seven days of November.
On the other hand, American Goldfinch numbers plummeted. We banded only 198 for the season (just 9 in September!). This is well below our 14-year average of 538 per Fall season and last year’s 1,316. What happened!? I don’t know for sure but I suspect that they were decimated by conjunctivitis (Mycloplasma gallisepticum), a disease that wiped out the House Finch population a number of years ago and is found in the family Fringillidae. We were seeing goldfinches with infected eyes in March, April and May and a couple we captured in September were showing signs of it but not nearly as bad as those we saw in the Spring. I can’t come up with any other explanation as it appeared to be an average food year for them and Summer weather was well within the norm. (While conjunctivitis is usually associated with House Finches it has been noted in American Goldfinches. One report I saw mentioned infected goldfinches in the mid-eastern United States. We have had some of our birds recaptured down there. I wonder if they brought it back with them…..) But it just wasn’t at Ruthven that there was a decline. When I questioned other birders and visitors that mentioned having bird feeders, I got the same answer: American Goldfinch numbers are way down. So something happened – something major – and my guess is that it was conjunctivitis.
But there were some other “funny” things happening as well. The numbers of “long-distance” warblers that we banded were all well below the September norm although short-distance warbler numbers, like Yellow-rumped Warblers, were up (e.g., the 603 Yellow-rumps that we banded was our 2nd highest total for that species). On the other hand, most species of sparrows/juncos banded were well above the norm. Normally we get the long-distance warblers in September and the other species late September through October. Weather-wise September was a good month so it’s hard to understand. And if there was a problem up north in the breeding area, one would think that warblers and sparrows would be affected similarly. Again, it’s hard to understand.
Another factor in regard to the consideration of the warblers caught is that our net hours this season (9110) were the highest ever. (Since I retired two years ago I have been ratcheting up our net hours – we will go forward now with the present array of nets….but there’s been a period of adjustment while we worked out what is manageable.) More net hours, one would think, should translate into more birds caught. But the number of birds caught per 100 net hours in September (23.89) was our lowest, and this was reflected in our warbler catch.
On the whole, we banded 4,605 birds (3rd highest total) of 81 species. Our rate of capture – 49.7 birds per 100 net hours was one of our very lowest. A comparative list of birds banded and a comparative summary will be posted shortly and will give folks interested in more detail a chance to look things over.
A banding station, in order to run effectively and efficiently, must have good volunteers. This season 48 individuals contributed 1,524 hours of their time to help us do the job. We owe them a great deal of thanks!
One of our primary goals is to educate the public about birds. This Fall we had 1,313 visitors,
We would also like to thank the Lower Grand River Land Trust and the staff of Ruthven Park National Historic Site for their ongoing support.