Stephane’s blog for April 29
A week to remember and celebrate!
There has been no more snow since April 25th, but the weather has stayed cold, with a frequent North wind. Nothing to entice bird migration and, indeed, it has been quiet since the last posting. Only this morning, Friday 29th, there was a short-lived movement, with, notably, a little wave of warblers, with our FOY Black-throated Green Warbler among all the Yellow-rumped Warblers.
When there are not many birds to keep us busy, it is time to dig into and play with the data. I wanted to put the first week of the current season into perspective. And since it is said that a picture is worth a thousand words, here’s a graph:
This graph represents the total number of birds banded between April 16 and 23 across the years, from 2002 to 2016. With almost a thousand birds, it is obvious that this spring has been exceptional to date. But wait, you might say, what about the effort put into catching all these birds – did it vary? Maybe the weather was so bad the other years that the nets were closed most of the time. Very good point! So, let’s look at how many “mist net – hours” were possible during this period. (We have an array of 15 mist nets potentially open 6 hours every day, so a maximum of 90 mist net – hours/day). Here it is:
(unfortunately, we do not have the 2012-13-14 data in a digital form).
So, there are obvious differences here as well: very, very little net time in the Spring of 2015 for the first week of that season. And 2004 and 2011 were not very good years either. But, overall, while there is some variation it is nowhere near as drastic as the number of banded birds. The first week of 2015 is very similar to 2009 and 2010, but not so for the number of birds that were banded.
Which leads to a third way of presenting the data: capture rate! It is simply the number of banded birds divided by the effort to capture them (that is, number of mist net – hours). So, here’s the third and final graph:
We can now easily see that the first week of banding in Spring 2016 was indeed extraordinary! The second highest, from 2009, does not come close and all the other years have very low capture rates compared to 2016.
The first week of banding in 2016 is, and will be, a week to remember! It is the nature of records to be one day broken. However, I would be ready to bet that this one might reign for a while!
Let’s end the post with more pictures: this morning, we captured a Brown Creeper with a deformed bill. It had the normal downward curvature, but with a turn to the right! I’m including a picture of a normal bill for comparison.
The Brown Creeper with a right turn in its bill
A Brown Creeper with a normal bill
The data for net hours is digitally recorded for all years at BPBO it merely needs to be compiled. The data is on the Cabot Head computer under the CMMN excel data file.