Wednesday, February 10, 2016

We are Eggs-pecting!

Sherri Elliott got some great vocals and video this morning at Ustream! After a few beaky 'kisses', Mom and Dad were heard copulating not far from the nest. While we don't have recorded video from Fort St. Vrain, the eagles there have been copulating as well. It looks like eggs are on the way in both places! Ustream highlight: We'll add a youtube video as soon as we have one for those of you on devices.

While we don't know when the eagles are going to lay eggs, we are entering the time period in which laying has historically started. In Decorah, the first egg has been laid as follows:

  • February 18, 2015 - first egg in 2015
  • February 23, 2014 - first egg in 2014
  • February 17, 2012 - first egg in 2012
  • February 23, 2011 - first egg in 2011

Note that 2011 and 2014 were very similar. All three eggs were laid on the same date those two years. 2012 and 2015 were both a little milder than 2014 (the Winter that Wouldn't Die) and Mom was just beginning to lay eggs in 2011. Personally, I'm thinking sooner rather than later...but even February 23 is just thirteen days away. While it is rare for bald eagles to lay three eggs, Mom has a history of doing just that! The breakdown is as follows:

  • 79% of clutches have two eggs
  • 17% of clutches have one egg
  • 4% of clutches have three eggs

In Fort St. Vrain, the first egg has been laid as follows:

  • February 14, 2015 - a first Valentine's day egg for 2015!
  • February 21, 2014 - first egg in 2014
  • February 17, 2013 - first egg in 2013
  • February 16, 2012 - first egg in 2012
  • February 16, 2011 - first egg in 2011

Although Fort St. Vrain is about 714 miles from Decorah as the bald eagle flies, the two sites have very similar nesting chronologies, with the Fort St. Vrain eagles usually leading Decorah by a few days and both females tending to lay three eggs. This is an interesting contrast with the Eagle Valley site, which is only about 50 miles from Decorah but was roughly a month behind the year our cammed nest was active. The female there only laid two eggs.

So what can we expect once the first egg is laid? The eagles will begin incubating immediately to prevent it from freezing. However, if the weather is relatively warm, we may see them spend a surprising amount of time off the eggs. Eggs need both an appropriate temperature (around 99 degrees) and appropriate humidity, so Mom and Dad will get up and down as necessary to control them. Adult eagles have body temperatures of 104 to 105 degrees, so they have heat to spare when it comes to incubation. We can expect the eggs to hatch in both places roughly 35 to 37 days after they are laid. If the past is anything to go by, the Moms will spend more time incubating than the Dads, although the division of labor varies from nest to nest.

Eagles are well-prepared to handle snow and cold, but weather has sometimes been an issue at the Fort St. Vrain site. While Fort St. Vrain is slightly warmer than Decorah in March (26-53F versus 25-46F), it gets an average of ten to eleven inches of snow as compared to Decorah's five and a half. Wet, heavy snow can provide a serious challenge to eaglets not old enough to thermoregulate, although the re-establishment of a prairie dog colony not far from the Fort St. Vrain nest means that hunting can be done a little closer to home.

We wish all of the eagle families well and are very much looking forward to the coming season! Bob would be so pleased with the success of N2B and our new camera systems! I'd like to think he approves.

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