April 2, 2013
On the Road Again..............
This picture shows my 1996 Subaru (262,000 miles) loaded and ready for a day in the fields. Traveled 121 miles today and checked exactly 40 boxes. Two starlings eliminated today. There are now 10 boxes with kestrels in the immediate area, but it is important to point out that does not necessarily mean that the birds sighted now will remain at those boxes and breed. There will be lots of shuffling, disappearances for a week or so, etc. before things finally settle out. The best indicator that a box is going to have breeding birds at it is when you repeatedly see pairs at or around the box. Currently there are 3 boxes with pairs at them.
Nestlings have been banded in my program for the last four years, but the problem with banded nestlings is that they have a very high mortality rate-reported to be 60%, 70%, or even higher- and they also have a very low degree of natal site fidelity. The last term refers to the fact that the following year they don't often return to the area where they were raised. These two factors mean that banded nestlings don't often provide very much in the way of hard data when trying to assess return rates, survival rates, etc. Breeding adults, on the other hand, are thought to more regularly return to their previous year's breeding area (maybe not the same box, however). It was with this thought in mind that I began seriously banding adults for the first time last year. I was hoping that by doing this I could shed some light on the very thorny problem of trying to figure out just who is sitting on the top of that box come March.
Today I was able to capture two adult females and was very pleased to see that the data I was hoping to collect has begun to trickle in. Since this blog is also serving as my personal journal for the year, I need to be using specific box locations when discussing various situations as they arise. This is not helpful to you, the reader, but is very helpful to my research. Sorry about that. At the Lipton Farm south box I captured a female that was unbanded. Since I did band the adult female that used that box last year, I at least now know that the bird currently at that box is not the same female as last year. The second female kestrel I captured was at the Grant Farm in East Windsor. Interestingly, she was the breeding female last year at a box that is 1.2 miles south of the box where I caught her today. So far, neither female is the same bird who used their respective boxes last year. Good information. Total miles traveled to date=744 total box visits to date=156
"Low degree of natal site fidelity" -- ungrateful kids! All kidding aside, this is pretty interesting stuff. It's okay that I don't know the specific box locations. Differentiating them by name is enough. Are you using a bal-chatri to catch the adults only, or is this used to capture kestrals of all ages?
ReplyDeleteHi Elaine- This is a bit complicated to answer. The nestlings are always banded just before they leave the box. There are typically no other attempts at catching and/or banding them while in their natal area during the remainder of that calendar year. The bal-chatri is used in the fall to capture birds that may be migrating through as well as in the early spring period that we are in now. Some of the birds captured now may just be moving through or they may be birds preparing to set up shop locally. Once the female is on eggs in the box, box trapping may take place. This is basically trying to capture them in the box for banding purposes. I am certain that there are some reading this who might have grave concerns with all this talk about "capturing" etc. and see it as a dangerous disruption to a CT threatened species of bird that is simply trying to breed and raise their young. The best way to guide conservation efforts with threatened species is with good, solid data. Without banding as many birds as possible, we simply have no idea of what their return rates, survival rates and patterns of dispersal/distribution are. Banding kestrels has been carried on for decades with no evidence of increased rates of nest abandonment or active relocation as a result of trapping/banding activities.
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