On June 19th, climber Teryl Grubb, US Forest Service wildlife research scientist headquartered at Rocky Mountain Research Station; Kendall Simon from University of Maryland (Environmental Health); Claire Weber from University of Maryland (Environmental Geography); and Emily Oja, a student from Michigan State University (Fisheries and Wildlife) came to Gratiot Lake to band this year's eaglets. Terry did the climbing while the other members of the team did the weighing, measuring, and blood sampling while the eaglets were on the ground.
The considerably larger of the two eaglets is a female. She weighed 9 lb 7.7 oz. and was approximately 32 days old. The smaller of the two is a male. He weighed 5 lb 8.2 oz. He hatched about four days later than the female.
Females are normally larger than males and the four day difference in age is also a factor, but the size and weight difference was more than would have been expected. As noted on the eagle page, this older sister had early on established dominance and attacked the smaller male when he attempted to be fed. He often received a much smaller portion and sometimes nothing at a feeding. This appeared to already be happening when we arrived June 1st. With last year's male pair, this meal-time dominance was noted also, but it began a couple of weeks later in their development, and they were more evenly matched in size.
Data gathered in this research is part of a long term studies by William Bowerman of the University of Maryland (formerly Clemson U.) The birds banded are part of a study monitoring the bald eagle population for over 50 years. The focus is upon heavy metals, pcb’s, and DDT in Great Lakes bald eagles as bio-indicators of overall environmental health. Feather samples yield DNA and show mercury, lead, selenium levels. Blood samples reveal levels of PCB’s and DDT. Various physical measurements are indicators of the overall health and development of the birds.
Select below to see a video from that year's eagle banding. The longer videos will require a high speed connection or you could start the download
and then go do something else for awhile. (Remember to close one video window before opening another.)