Eagles

My Ornithology class had some great views of bald eagles this week near Woods Reservoir.

Adult bald eagle. Photo taken by Jamie Sue Wilson who is enrolled in the class.

Adult bald eagle. Photo taken by Jamie Sue Wilson.

In addition to two adults, we saw a couple of young eagles circling overhead.

Immature bald eagle. Photo by Jamie Sue Wilson.

Immature bald eagle. Photo by Jamie Sue Wilson.

Immature bald eagle. Photo by Jamie Sue Wilson.

Immature bald eagle. Photo by Jamie Sue Wilson.

Bald eagles take four years to reach full adult plumage. The individual shown above is likely a second or third year bird. For two great overviews (and some fabulous photos) of the maturation sequence of eagle plumage, see Ron Dudley and Mia McPherson’s pages.

The two adults were nesting: one sat in the nest and one stood close by in the tree. Until recently, such a sight would have been very rare in Tennessee. In 1990, only sixteen nests were known in the whole state. Now, there are at least one hundred and seventy five nesting pairs of eagles in Tennessee.

The population increase in Tennessee is part of a nationwide trend. After decades of decline caused by shootings and poisonings (encouraged by bounties), followed by the impacts of DDT, bald eagle populations have edged higher year-by-year since the 1970s. In 2007 the species was removed from the federal list of threatened and endangered species, although it (and its cousin, the golden eagle) remain protected by other laws.

Bald eagle nests are huge: brush piles crammed into the crowns of high trees. Nest-building can take up to three months, although when pressed the birds can slap something together in a few days. Most clutches have just two eggs (a few have one or three). Both male and female incubate the eggs, although the female does most of this work. Between them, the parents keep the eggs covered by a warm body for 98% of the time. Eagles are relatively heavy and they have sharp claws, so the parents take extreme care in the nest, walking around the eggs with clenched feet.

The incubation period lasts 35 days; the young leave the nest two to three months after hatching. These young birds stay with the parents for a variable period, from a couple of weeks to several months, then set off on an extended period of wandering. During this unsettled stage they have no fixed territory but move around, presumably seeking food and, later, mates and a good place to nest. The immature birds at Woods Reservoir are likely in this wandering stage.

The return of nesting eagles to the U. S. has intersected with the internet age to produce a new phenomenon: the eagle cam. You can now follow the adventures of nesting eagles from your computer, an activity that is usually considerably more compelling than working through your email inbox. So, be warned, there is a reason why some of these websites get millions of viewers… Here is one in Florida with two eaglets (hatched back in early January).

16 thoughts on “Eagles

  1. Elizabeth Dornbush

    Once rarely seen here, about 250 miles north of Toronto, bald eagles are now nesting in several sites within a seventy-five mile radius and we are seeing them more frequently. They are always an awe-inspiring sight! Thanks for your infotrmative links.

    Reply
  2. Robley Hood

    Thank you for providing so much information in this post, David. The only eagles I have ever seen in the wild were in the Everglades and then they were at a great distance. I know where I must go now!

    Reply
  3. Peter Thoem

    The Royal Botanical Gardens near Toronto, Ontario is closely watching a young pair that has attempted breeding for the past 2 years. Two years ago they courted and built a nest, but then nothing, last year they incubated 2 eggs but in the end abandoned the nest. We hope this is just immaturity and keep our fingers’ crossed for 2013.
    Like Tennessee and your ‘nationwide trend’ Ontario has seen an encouraging increase in Bald Eagles, where once there were maybe 2 pairs, now there’s many. They also overwinter around here.

    Reply
  4. Bill

    Bruce Baird showed me these after church this morning. Said he is really enjoying the class (no doubt). Counted 35 sandhill cranes, flying in formation, over my house on Saturday. Actually knew what they were before I saw them (heard them in the distance)!

    Reply
  5. dale and jeannie swant

    Once the chicks hatch the interactions with the immature eagles get very tense and acrobatic – or I quess aerobatic is the right word. We have seen this a number of times and the breeding pair of red-tailed hawks have also be very brave to spar with this pair of eagles. We saw this one time with Bill and Marcia Clarkson-most exciting!

    Reply
  6. David Robertson

    David: This comment has absolutely nothing to do with spotting eagles; instead, I’m soliciting your professional opinion.

    I manage an 810-acre wooded preserve in the northern Piedmont in Pennsylvania. We are in a suburban neighborhood and the preserve was assembled over a period of 40 years from nearly 100 separate parcels of land, each of which has a different land use history.

    One of the parcels had been a 10-acre apple orchard located hard-by a woodlot full of very old trees. When the orchard was abandoned, a woodland returned to the site, but the new woods consisted almost exclusively of early-successional black cherries. As you know, black cherries are relatively short-lived, and these trees are now mature and beginning to senesce. Furthermore, the woodland has no understory or shrub layer other than invasive plants like multiflora rose, an extraordinarily aggressive Asian grape called porcelain-berry, and Microstegium. So, in sum, the woods is like an aging savannah with a highly disturbed understory of invasive plants.

    One of my land managers has suggested to me that we harvest the good, large, mature black cherries to maintain their value as lumber, and to return any proceeds from the sale to reforesting the site with native trees that will reach canopy status like oaks, hickories, tuliptrees and American beeches. (The woods is easily accessible from an adjacent farm field; forest harvesting machinery would not disrupt any of the nearby old forest.) Because we have a large deer herd, newly planted trees will have to be protected from browsing and antler rubbing, meaning that the site will have to be enclosed in a fence (expensive) or the new trees will have to be protected in wire cages, requiring more routine stewardship work for many years for my small staff.

    I fully recognize the value of dead wood for returning organic matter to the soil and for providing habitat for all manner of organisms. However, if we allow the woods to deteriorate, the trees are going to die and fall, the forest floor is going to be covered with trunks like scattered pick-up-sticks, the vines and invasive shrubs are going to re-surge, and the fallen trees will preclude us from controlling the invaders–even if we decide to try reforest the site.

    I’d value your opinion about what I ought to do, if you’re willing to share. You could reply to this comment, or you could email me directly at JOSHWLWGRV@cs.com. Thanks!

    David Robertson

    Reply
    1. David George Haskell Post author

      Hi David,

      Thank you for your work on this land. It sounds like a fabulous place. And you thoughtful approach is undoubtedly of great benefit.

      I’m hesitant to offer any advice without seeing the site or knowing much about the particularities of the region’s ecology. In general though, if you harvest the trees you’ll open up light and the understory invasives will really take off. But, as you point out, that may happen with the maturation and death of the cherries.

      Black cherry can live for 100+ years, so depending on the age of the trees, what you’re seeing *might* be natural thinning out of the saplings as a few dominant trees take over. (Again: I’m working in the dark here). If that is the case, you could also leave things as they are and succession will proceed (slowly).

      The presence of invasives and of deer complicates things. All over the eastern US, these two factors (along with changed fire regimes and climate) are pushing forests in directions that are hard to predict, creating communities that have not been seen before. So there is a balancing act between fighting off the deer/invasives and accepting that the forest is headed in new directions and we can only do so much to help maintain native species. Where that balancing act comes out depends, in my view, on the values that we hold for the land (what are the management goals — native biodiversity? income? recreation? scenic values?) and the constraints (time/money) that we’re under. Having spent a considerable amount of time working on invasive privet eradication, I have a sense of how many hours it can take to “clear” even a small area. Multiflora rose is terrible stuff to try to get rid of. Around here, though, maples and some other trees will grow out of the shady core of thickets (sometimes) and overtop the rose.

      Those are some rambling thoughts. They are all things you likely know very well, so I apologize if I’m rehashing familiar arguments. I guess my bottom line would be figure out exactly how much money and time a good reforestation (with oaks, etc) effort would take. A combined/experimental approach might be interesting — harvest some areas and not others (but there may be economies of scale working against you there)?

      A colleague of mine here, Dr Jon Evans, is from PA and knows the area’s forests well. He might have additional insights.

      With many thanks, David

      Reply
  7. David J Robertson

    David: Many thanks on your thoughtful reply. We had a forest harvester come to look at the black cherry stand, and he said that harvesting all the mature cherries would generate only $3,000, which we would have to divide evenly with him; clearly it’s not worth the trouble.

    In our experience, stewarding/shepherding a new forest from saplings to the point at which we can stop doing intense, routine maintenance because of the invasive plants and the deer is 20-25 years. $1,500 would barely cover the purchase of the trees, let alone the follow-up maintenance.

    We’ve decided to reforest the area with the mature cherries in place, hoping that the cherries don’t crush too many of the newly planted trees when they inevitably fall.

    Reply
    1. David George Haskell Post author

      Hi David, Thank you for this update. One more thought: old apple orchards sometimes have great morel production. Eugenia Bone’s excellent Mycophilia book has an amusing discussion of a foray into an old orchard.

      Reply

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