At the end of October the morning monitoring group began picking up and examining pellets at the burrows to confirm what the owls are eating. A trend of insects and not rodents has been established. Being next to agricultural fields, it was expected for rodents to dominate their diet. At first we wondered if the farmer was putting down a rodentcide. Greg Clark recently discovered a researcher, in the Imperial Valley where 70% of California’s burrowing owls reside, who found only .2 % of pellets contain rodents. His explanation is that the flood irrigation eliminates rodents. Maybe this is what is happening here as well.
Not knowing if insects could sustain our remaining 5 owls through the winter, I was convinced to do a short-term supplementary feeding of frozen white mice. I began this on January 16th. Greg and I decided we should learn something from doing this as well. I first wanted a basic question answered – how long will it take a mouse to be regurgitated? Answer: 2 to 3 days. Greg suspected that the owls were not regurgitating all of their pellets at the burrows and if so, we thus were not seeing all that they eat. This has turned out to indeed be the case. Only a small percentage of the white mice pellets are showing up. Some weeks more than others. And those that we do find are a combination of mouse and insects, sometimes very packed with insect parts. I am feeling better that they are finding insects in the winter.
Now onto the owls themselves. 90X is her usual, confident self residing at #50, although of late she can be seen all the way down to #37 in the afternoon. This is due to the fact, I surmise, that 88X has not been on site since 1/9 and #37-46 was her “territory”. No signs of predation in the park this time as was the case with the last two owls. The female of the local pair at #15-16 has not been seen since 1/9 either but because she is so secretive and because it has been so cold I’m not completely convinced she still is not there. The really AWESOME news is the release site local owl who I had started to suspect was male has joined 90X at #49-50. Last week a regular park walker and the evening monitoring group saw them together at #50. Courting behavior was going on and the male has been named Whitebeard. (He really extends his white chin feathers very long when doing a courting display). This morning we watched Whitebeard come out of #49 and 90X out of #50. If you go out to see them Whitebeard flies easily if approached too close.
A decision on whether more owls will be relocated to Zanjero this Spring is still being reflected upon. Greg Clark is waiting to hear the information the farmer has, how stable the food supply is, and how many migrants will arrive on site in February into early March.