Dr. Charles R. Preston, Senior and Founding Curator, Draper Natural History Museum, Buffalo Bill Center of the West in Cody, Wyoming
06 July, 2010 – Summer seems to have disappeared after only a week or so! Today, we have rain, with high temps in the 50s. Many of our birds are beginning to successfully fledge, and a few have left their nests before being able to fly. These birds will stay in the vicinity of their nests, and barring predation, human interference, or exposure, the parents will continue to provide for them until they are able to fly away from the nest area. I was able to capture and band a couple of these birds last week, and as of today they are still doing well in protected areas under the nest. These two were just too big to share the nest platform any longer.
Richard Jones completed his aerial survey last week. We will do some ground-truthing later this week, and I’ll compile our results for you next week. Although nest occupancy was down considerably this year, the success rate productivity of occupied nests appears to be higher than last year. An analysis of weather data and relative prey abundance during the past two years may help us understand the year-to-year variation in nest occupancy, success, and productivity. It will be especially interesting to relate landscape composition and human activity with nesting dynamics as our study continues. Will eagles demonstrate significant prey-switching behavior as our robust rabbit populations begin to decline, or will there be a significant reduction in nesting effort and success? Are prey and vegetation characteristics different in areas of the Bighorn Basin where nesting eagles are absent? These are some of the questions we will be addressing as more information becomes available.
Here are some of the reports I received this past week from our Golden Eagle Posse nest monitors:
Report from Anne Hay and Richard Gruber on 01 July: We had an interesting day at the nest, with enough activity to make the six hours move by quickly. Our oldest chick was seen exercising its wings a number of times while jumping from one side of the nest to the other. I suspect this one will soon fledge. The youngest chick, however, has a lot of spunk. One of the adults flew in with a small rodent, and both chicks pounced on the parent, so that it looked like a ball of eagles. Seconds later, when the adult flew away, the youngest chick was mantling the prey. The oldest chick did not put up any challenge for the rodent, and after standing near the smaller, mantling chick for a short time, just moved to the north side of the nest. The youngest chick then picked up the rodent by its long tail, and moved quickly to the south side of the nest, where the rodent was quickly eaten. Besides this prey delivery, there was also some type of prey already in the nest when we arrived that both chicks took turns feeding on, and later in the morning an adult flew in with a medium sized prey that was actually fed on mainly by the adult, as the chicks looked on.
Report from Richard Brady on 01 July: I checked the nest with my scope and looked around the area with binocs but no bird was to be found! There were the usual pigeons and what appear to be swallows flying around but all at once I saw what I thought was an adult bird doing the circle the valley below, so I noted the time and wrote that down! When I looked back up there was a bird sitting on a ledge high point looking around! I moved the scope from the nest to this bird to find out that this is our last chick which I believe is a boy bird given its smaller size! This bird walked to several other perches while I was there and when a breeze blew on him there was still some white feathers to be seen! I stayed the full 2 hours watching this bird but it just sat looking around at other small birds and sort of weaving…has to be our guy!!!!
Finally, a report from Rosemarie Hughes on 04 July: As I drove up I saw an adult flying away from the nesting area. I didn’t get a chance to see if it was with the chicks or not. When I was in position, I could hear lots of chirping from the smaller chick. The large chick wasn’t even close—I had to look around. Couldn’t see it so drove a little closer. There it was, about 10 feet east of the small chick and the landing. The large chick was sitting in front of some food. I could see the red of the meat plus a little something hanging from the beak. I lost sight of the large bird. I knew it didn’t fly away or roll down the hill. At this point the larger chick looks almost like an adult—from the backside anyway. Really dark. There was lots of movement today. The small chick walking along the landing, the large chick actually flapped and hopped itself back to where the small chick is so they are together, at the end of this day anyway. Both in the hot sun.
Many thanks again to all of our Posse members. I can’t include all of your reports each week, but I do read them all and look forward to following your progress. Just a reminder, your data sheets and field journals are due when your adopted eaglets fledge. That will be soon for some of you! Stay tuned for further updates next week. Best wishes, C.R. Preston
