Fifteen years of video cameras on Bald Eagle nests from 2006-2020 provide a wealth of information on eggs, chicks, fledges, clutches, and broods, numbers that beg for statistical analysis. I’ve spent several weeks (well, months, actually) crunching numbers for each of those years and have come up with several pages of tables of stats accompanied by summaries and discussion.

An introductory page sets the stage with an overview of the nests included in my study, 401 breeding efforts at 85 nest locations across North America over 15 years.

The first page of data in the series, Eggs, Nestlings, and Fledglings, presents a Table with all the numbers and a narrative analyzing them. Teasers:

• • 2-egg clutches were in the majority, making up almost 61% of all clutches. Only about half that number, 31%, had 3 eggs, and fewer than 7% had 1 egg.
  • 3-egg clutches were the most successful in producing at least 1 hatchling, while 1-egg clutches were least successful.

The next page, Success Rates of Clutches and Broods, further explores the clutches of eggs and broods of eaglets and how successful they were, with a new Table showing the numbers. Teasers:

• • More than 87% of the clutches overall produced at least one hatchling — a “successful” clutch.  All of the eggs hatched in more than 66% of them — what I am calling a “perfect” clutch.
  • Of broods of eaglets, nearly 77% were “successful” in producing at least one fledgling. An encouraging 47% of the broods resulted in all of their eaglets fledging — a “perfect” brood.

A new page digs down into Lost Eggs and Failed First Clutches of Eggs, with 2 Tables of data. Teasers:

• • Just under 21% of all the eggs were lost.
  • Over 55% of the lost eggs occurred in 1-egg clutches.
  • The cause was unknown in more than half of the lost eggs. Of the known causes, intruders at the nests made up the highest percentage (almost 13%).
  • A little more than 11% of the clutches of eggs produced no hatchlings. Almost half of these were failures of 1-egg clutches.

The following page, with 2 more Tables, similarly surveys Lost Nestlings and Failed Broods of Eaglets. Teasers:

• • Of all nestlings, almost 21% did not fledge.
  • A large plurality of losses of nestlings had no obvious cause.
  • Unlike with lost eggs, the largest percentage of known causes of lost nestlings was not nest intruders but bad weather.
  • The number of failed broods of eaglets was relatively low: Only about 9% of the broods of eaglets lost all of their nestlings before they could fledge.

These data do not show consistent trends from year to year, either in numbers or in percentages. Some years are more successful in hatches and fledges than others. Nothing in the data suggests that things are getting better or worse for Bald Eagle breeding.