Featured Families

I've decided to name the house wren family series "Featured Families". This is where I will be closely following two pairs of wrens and their offspring (babies). The first Featured Family is the pair of wrens living in the territory labeled C2.

Hurray! The picture on the left is how the nest looked yesterday. The picture on the right is the view from today. The female laid the first egg today.

Here is a close up picture of the first egg. I labeled it number 1. House wrens only lay one egg per day. We
label the eggs to determine the laying order of the eggs. They are labeled with a permanent marker. It is not toxic to the embryo (baby growing inside of the egg) and doesn't appear to have any side effects on the development of the offspring. House wrens in our population in Michigan lay 5-7 eggs on average per clutch (this is what we call the group of eggs in the nest collectively). However, they can lay up to 9 eggs per clutch but this tends to be rare.

Why don't they always lay 9 eggs if they can? That is a lot of mouths to feed. It takes lots of work, time and energy to feed the offspring. The more offspring they have, the more work they have to do. That takes a toll on their bodies. Think about all of the other things they could be doing instead of feeding 9 offspring. They could be feeding themselves, looking for their next partner, chasing away other birds from their territory etc. Also, sometimes there are just not enough resources (food) for all of the offspring. I could go on and on about the different choices, strategies and theories regarding parental care and finding the optimal number of offspring, but that should be enough for today.

Completing The Nest

Continuing from the house wren nest building series from last year...

So once the male has completed building the nest and paired with a female, she will line the nest box with soft things to create a cushion for the eggs. Often females will lay grass, pine needles, feathers and hair (from deer, dogs, etc.) all around the cup of the nest. Sometimes we will find some rather unnatural soft lining materials the female will put in her nest like foam, plastic and ribbon.

After the nest has been lined, eggs are usually on the way. However, when she starts to lay eggs differs for each female. Some females will line the nest and lay an egg the following day. Others can line the nest but it may take a week before the female will lay an egg.

This year, we will follow two pairs of house wrens from when the female lines the nest to the fledging (when the young leave the nest) of their offspring.

The first pair of house wrens live in the territory labeled C2. She lined the nest yesterday, May 12, 2010.

The female has lined the nest with some grass, dried tufts and a couple of feathers. Today she continues to line the nest adding a few more feathers and grasses to the lining of the cup.


Any guesses when she will lay her first egg?

An Easter Egg Hunt in May

I found two nests yesterday that both had 2 eggs on Saturday but the nests lay empty on Sunday. Sure enough today there was new egg in each nest. What could have happened?

1. The nest could have been predated. A predator got into the nest and ate the eggs.

2. Another female could have chased away the first female, tossed the eggs of the first female and then laid her own egg the following day.

I'm not really sure which scenario happened but it brings up how aggressive house wrens can be. House wrens will take over a nest from other birds like the eastern bluebird. They chase away the owners of the nest and toss the current eggs from the nest. They will stab the eggs with their beaks and literally throw them out the door. A couple times I have found the eggs laying at the base of the bird box with little holes in them.

However, this time, I didn't see any eggs close by to be able to draw a firm conclusion. Any thoughts?

New Field Assistant and Some Eggs!

Today was a rainy day out in the field. I go out rain or shine! The weather just determines what we can do out in the field. Today three nests laid eggs. It's starting...

Speaking of which, I'd like to introduce my new field assistant for the summer of 2010. Meet DJ McNeil (pictured above). He has finished 2 years at Kellogg Community College in Battle Creek and will be starting his 3rd year of undergraduate school this fall at MSU. This past spring he has been working at the Kellogg Bird Sanctuary. He's coming to me to learn about behavior and get more research experience. This July, he'll start his own independent project on some aspect of behavior with house wrens. In his spare time enjoying photography. Till tomorrow.

Bird Boxes Go Up for 2010!

Hello all! Well, it's spring and research is moving back into the swing of things.

Bird boxes went up the first weekend in April. Thanks to my bird box crew (pictured aboved...enjoying lunch together). Here is one of them putting up a bird box. We put all 204 bird boxes up in a few hours! All 68 territories were ready to go.

The males have been trickling in since mid-April and a few females have returned. Currently, no eggs yet! The house wrens are running about a week behind than usual. Not quite sure why but may be it's the weather...

Gone for the Winter

Sorry I haven't updated but I'm currently in the lab working on sample recovery. I'm running my radioimmunoassays on my yolk samples to get my testosterone levels. See you in the spring!

Nest Construction

Hi! I've been very busy in the field. I will try to be more on top things. Rather than cram a lot of information, I'm just going to be back logged in entries for a bit. Let's return to the nest building basics.



The males return first and begin to build the base of the nest. They add lots of sticks slowly building up to whatever height they choose. There is no particular height requirement.

The sticks are placed randomly on top of each to create the base or they start to create a circular pattern (above). In this picture to the left , the sticks are stacked about 1 inch high from the bottom of the nest box. From my experience, they tend to build nests from 1-7 inches high (the highest is right at the opening of the box.

Males eventually will create a cup shape at the top of the nest when they have almost reached their desired height. The picture below is of a nest about 4 inches tall. Then the male has completed his portion of the nest building and await to be paired with a female.