Thursday, December 29, 2016

A trip down memory lane: Favorites from 2016, Decorah edition!

It is time for a look back at 2016! We asked the mods for their five (or more) favorite moments of 2016 from Decorah and Decorah North. We will feature favorites from Decorah today.

Several mods mentioned ‘firsts’: first pip, first hatch, and first feeding. A few favorite firsts from 2016.

  • First feeding for D24: Mom Feeds D24 Sweetest Thing: https://youtu.be/hOdii7wjh_s
    It is reassuring and sweet to see an eaglet’s first feeding.
  • First pip for D25: D24 & D25 pip with beak moving - super close macro zoom: https://youtu.be/lPjOHCLa4hA. A feeding for D24, one of our first glimpses of D25, cute vocalizations (I can’t help but think of baby talk), and birdsong everywhere.
  • First glimpse of D25’s face: https://youtu.be/N49xo52cPOU. Does this video also show D24’s first PS? Wonderful if brief views of D25’s tiny talons and face, down still wet from hatching, and D24 gobbling down sucker roe!

Poopshoots remain a perennial favorite among mods and watchers alike. Two poopshoot moments really stood out for a few moderators…


There were a lot of miscellaneous favorites – cute, interesting, or fun glimpses of daily life at N2B!


We all missed D24 and D25 after they left N2B. But the cameras at N1 and Robin Brumm’s videos gave us a glimpse of their post-fledgling lives.


All of the mods mentioned followers, classrooms, and/or people at After the Fledge. They loved the chance to interact with classrooms, our guest moderators from teamcarnes’ class, the daily chats with followers, meeting and hanging out with eagle friends and family at ATF, and getting a chance to see Ambassador in Training Decorah (widely believed to be D20 from 2014): https://youtu.be/NZELDqr4OfQ

Judging from readership of blogs, your primary Decorah-related concerns in 2016 were:

Have a very happy new year and thanks for watching with us in 2016!

Thursday, December 22, 2016

Nesting Chronologies

We were asked about the nesting chronologies of bald eagles. While nest timing can very from region to region (Florida, for example, is quite different from Iowa), mark your calendars as follows!
  • In the nests we watch in Iowa and Colorado, bonding and copulating behaviors become more pronounced and frequent after the winter solstice. Female eagles begin laying eggs 5-10 days after productive copulation begins. This usually happens in mid-February at the Decorah and Fort St. Vrain nests. The Norths have a slightly later chronology and probably won't lay eggs until mid-March.
  • Each egg is laid about 3-5 days apart, and incubation starts with the laying of the first egg.
  • Eagle eggs begin hatching roughly 35 to 37 days after they are laid. This usually begins in late March in Decorah and Fort St. Vrain, and mid-April at the North nest. Hatch can take more than 24 hours for any given egg.
  • Eaglets spend 75-80 days in the nest before fledging. This usually happens in mid to late June at the Decorah and Fort St. Vrain nests, and early to mid-July at Decorah North.
More on the subject! 
Eagles have been observed mating ten months out of the year, but they only produce eggs and sperm for a very brief period of time after the winter solstice (see this blog for more on that topic, or this blog for a graph of daylight length rate changes). Between solstice and egg-laying, watch for female eagles to foot and nibble males, vocalize at them, rub against them, and even mount them to indicate receptivity. Males will increase the amount of material they bring into the nest, work on the area that will underlie the nest cup, and vocalize at and with females as both sexes become more vocal. Listen for the unique and wonderful sound of the eagles vocalizing together!

A quick primer on egg fertilization in birds. Sperm needs to encounter an ovum at the infundibulum, or site of fertilization.  If sperm are too early, they will die prior to the arrival of an ovum. If sperm are too late, they can't penetrate the eggshell layers that form around the ovum in the female's oviduct. So how do birds assure fertilized eggs? They:
  • Copulate regularly. Regular copulation helps assure a good supply of sperm - especially important in an animal that regularly clears its cloaca when eliminating waste!
  • Store sperm. Sperm storage tubules maintain sperm viability, prevent stored sperm from being ejected, and continuously release sperm to the infundibulum.
  • Concentrate sperm at the infundibulum. Released sperm are passively carried to the infundibulum. Their continuous release and relatively slow drift help ensure that sperm are present when an ovum arrives.
Incubation starts immediately after egg laying begins in mid-February to early March. Eggs shouldn’t get too cold, but they also can’t get too hot, or the embryos will die. Adults sit on the eggs when they need heat and get off them when they need to be cooled. Both parents have a brood patch, a natural thinning of the abdomen feathers caused by hormonal changes, where their skin is in direct contact with the eggs to transfer warmth. Since incubation starts from the time the first egg is laid, eggs will hatch about 3 days apart in the order they were laid. Both the male and female take turns incubating, but the female, being larger, takes the longer incubation periods overnight. It is believed that her larger body weight makes her a little more tolerant to cold - important during a long inactive spell!

Once eggs start hatching in late March to mid-April, it can take longer than 24 hours for any given eaglet to complete hatch, although it doesn't tend to take that long in the nests we watch. We will announce hip or Hatch In Progress watch on Facebook, Twitter (@RaptorResource), and our website (www.raptorresource.org).

Saturday, December 17, 2016

Helping birds in winter!

After one of the nicest falls I can remember, winter has finally arrived. While the eagles are more than capable of handling snow and cold, I like to help (and watch!) smaller birds like chickadees, nuthatches, finches, redpolls, pine siskins, and other visitors to my yard. Here are a few tips to make winter a little easier for the birds and more enjoyable for you!

Like IHOP for birds. Looks like I need to fill the feeders again! 
  • Feed the birds! Winter is a great time to feed high-fat, high energy foods like suet and sunflower seeds. I have five feeders right now - two finch feeders (which include sunflower chips, thistle, and millet), a platform feeder with black oil sunflower seeds, a square box feeder with 'cardinal food' (black oil sunflower seeds, sunflower kernels, safflower seed, and peanuts, which also bring in blue jays and red-bellied woodpeckers), and a suet feeder. With different styles of feeder and different food choices, everyone can find something they like!  Remember, it is important to feed regularly once you have started. According to the Cornell Lab of Ornithology, little birds like chickadees can lose 25% of their body weight on a cold night. If birds come to rely on you for a constant supply of food that isn't available when storms hit or the cold really starts to bite, they might not survive.

    I had roughly 61 birds at my feeders this very cold morning, including a male cardinal, juncos, gold finches, chickadees, a sparrow, hairy woodpeckers, downy woodpeckers, red-bellied woodpeckers, and a white-breasted nuthatch. A quick tip: more perches can mean more birds. If you can't set up feeders near trees, you can install additional perches near your feeders. And you can also...
  • Plant and landscape for birds! We are fortunate to have a lot of trees in our yard. The feeders are set up near two cedars, which provide nice, thick cover; two elms, which provide a lot of branches for perching; and an oak woodlot. We left part of the woodlot unmowed this fall, which means plenty of vegetation for perching and additional seeds for small foragers. If you can, plant native shrubs and bushes and leave some tall vegetation standing to provide cover, food, and perches for wintering birds.
  • Install roost boxes. Another suggestion from Cornell. Roost boxes will help protect any birds that nest in boxes or cavities, including bluebirds, chickadees, titmice, nuthatches and small woodpeckers. A good roost box keeps the birds' body heat contained, has interior perches, and can be placed on a metal pole or wooden post. They are available in stores, or you can make your own. Follow this link for roost box-building instructions. Note: I haven't tried this since we have trees, brush piles, and outbuildings. But I plan to build one over Christmas break - it looks like a great idea and I would love to monitor one during cold weather!
  • Water birds. Let's get something straight: It is not true that heated bird baths kill birds. I don't know how many times I have been told not to water birds because they will get water on their feet or feathers and freeze to perches or become encased in ice. Not true! Flowing water is a valuable commodity in winter and heated bird baths will help birds while attracting more of them to your yard. Make sure to keep them cleaned and filled if you commit to watering.
Here's to a very happy and well-fed holiday to all of the birds! Looking for a holiday craft activity for children? My kids and I used to make these easy and inexpensive bird treats: http://www.education.com/activity/article/christmas-cookies-birds/. A little warning - this craft is fun, but be prepared for clean-up!



Did you know? Another bonus to feeding birds - you can join Cornell's Backyard Bird Count! Learn more about it here: http://gbbc.birdcount.org/. I plan on counting birds and watching for eggs in Decorah!

Tuesday, December 06, 2016

Report on the Unhatched Eagle Egg from N2B

Unhatched egg, N2B
We received the results on the unhatched egg from N2B. As watchers might recall, one of the eggs failed to hatch. We thought the embryo might have died early in formation, but according to tests run by Iowa State University, the egg was never fertile. How could that be?

A quick primer on egg fertilization in birds. Sperm needs to encounter an ovum at the infundibulum, or site of fertilization.  If sperm are too early, they will die prior to the arrival of an ovum. If sperm are too late, they can't penetrate the eggshell layers that form around the ovum in the female's oviduct. So how do birds assure fertilized eggs? They:
  • Copulate regularly. Regular copulation helps assure a good supply of sperm - especially important in an animal that regularly clears its cloaca when eliminating waste!
  • Store sperm. Sperm storage tubules maintain sperm viability, prevent stored sperm from being ejected, and continuously release sperm to the infundibulum.
  • Concentrate sperm at the infundibulum. Released sperm are passively carried to the infundibulum. Their continuous release and relatively slow drift help ensure that sperm are present when an ovum arrives. 
After removal from N2B
It is good to know that egg number one didn't contain an embryo, but why wasn't it fertilized? Three suggestions based on a simple idea: sperm wasn't present at the infundibulum when the first ovum arrived. 
  • While eagles have been observed copulating ten months out of the year, males don't produce sperm year round and they don't store it very long once production is underway. Perhaps Dad wasn't producing sperm in time for Mom's first egg. Sperm production is not required for pair bonding.
  • Mom may not have had enough sperm stored to concentrate sperm at the infundibulum in time for ovum #1.  
  • Age might be impacting reproductive success in either Mom or Dad. While free-living animals don't tend to have 'menopause' - a long stretch of time in which they do not bear young - age does impact fertility.
Some watchers have expressed concern that age might be a factor in the failure of egg number one. It isn't especially likely in Mom based on what we know. In general, a female bird that produces a healthy, intact egg is most likely fertile. Reduced fertility in our 'elderly' female peregrine falcons tends to be accompanied by changes in the amount of eggs laid, egg color, shape, and condition. Eggs might be unusually colored, pitted, or shaped - all things we saw at Xcel Energy's Sherco facility in 2014 and 2015. While we don't have a lot of data about senescence and egg production in bald eagles, wild eagles are generally assumed to live for 20-30 years. Given that Mom is just fourteen years old, age-related fertility impairment seems unlikely. 

So how about Dad? We believe he is at least 19 years old, although we don't know exactly how old he is. Senescence and sperm production in birds is a little complicated. Research indicates that aging impacts sperm quantity, quality, and motility in birds, and eggs fertilized by older males hatch at reduced rates when compared to those fertilized by younger males. But even with reduced motility, the sperm of older males tends to perform better than the sperm of younger males in a female bird's body. In short, older birds have less sperm than younger birds, and the sperm they have is less motile and of lower quality. But studies have found that older birds are more likely to fertilize eggs than their younger counterparts, even if those eggs are less likely to hatch.

Why are older male birds more successful at fertilizing eggs? The study Senescent sperm performance in old male birds found that obstacles to sperm movement in a female bird's reproductive tract affected older males less than younger males. I would love to see research on the role that skill and pair bonds play in sperm retention (I am defining 'skill' as actions taken by the male to assure a high degree of receptivity in his partner). We know that at least some female birds are able to preferentially reject the sperm of less desirable males, that female birds who mate with familiar males often produce more fertilized eggs with more egg mass than those who mate with novel males, and that the success of novel mating is highly dependent on male behavior. Reproduction is clearly much more complicated than we used to think, and it is obviously past time to drop the pejorative term bird-brained!

Having said that, we are back to the question of Dad's fertility. One infertile egg doesn't really give us enough data to come to any conclusions, but it is very helpful to know why the egg didn't hatch. We will be documenting whether or not nest production continues to decline at N2B. Thanks to John Howe, Kike Arnal, Pat Schlarbaum, Dr. Ensley, and Iowa State University for giving us more insight into the lives of the birds we follow. We are hoping for the best for our beloved Mom and Dad!



Did you know?
  • Sperm competition can result in speedier sperm among animals that have multiple mates while ovulating. Female mice, for example, take multiple mates and can't reject or store sperm long, so speed is important! http://www.sciencemag.org/news/2014/04/scienceshot-how-make-speedy-sperm
  • Why didn't the egg explode? A decomposing embryo rapidly produces gasses that can explode an egg, but this egg didn't contain anything except (presumably) Mom's blastodisc. It was also kept relatively cool and protected from direct sunlight by grass and nest detritus. John really had to dig for it! He told us that he dug through roughly a 5-gallon peregrine gravel pail worth of stuff to find the egg, including a squirrel's skull!
  • Would a receptive female in a long-term pair be likely to produce more eggs? I had very little time to follow up on the question, but here is one study that touches on it:
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2817173/
Things that helped me learn about this topic
So does this mean it is clearly the magic in Dad's many, many sticks? ;) All jokes aside, Dad spends a great deal of time working on the nest and providing food, although Mom is more than capable of building and hunting on her own. We tend to define the reproductive season as starting at the beginning of active copulation or egg-laying. But today's daily activities help cement the bond between Mom and Dad and may result in increased productivity months from now: more fertilized eggs with higher egg mass, more hatched eggs, and heavier weights in nestling eaglets during critical stages of growth. We are learning that eagle reproductive success depends on far more than the brief period of time they spend engaging in productive copulation.