My Montana

My Montana
My Montana

Wednesday, July 1, 2015

The Lives of Tree Swallows

 The refuge has been collecting data on bluebirds from a 50 box trail.  It is to study mountain bluebirds but we also keep track of what other species use the boxes.

The two other species that use the boxes here are tree swallows and house wrens.  Tree swallows are considered "bad" by many people because they compete heavily with the mountain bluebirds for the boxes.  But I love watching them and seeing how beautifully they decorate their nests. And they are of greater conservation concern  then are bluebirds, so we do need to be providing nest boxes for them.

The pair from box 19E - taken last year but one of my favorite pictures

The bluebirds got here before I did,  and my first assignment was to do my first survey, and repair/replace any boxes that were damaged.  We have a big mountain that shadows the eastern part of the trail so the first nests are always in the far western boxes.

The tree swallows arrived just after I did and immediately started competing for boxes. In a few cases, they actually moved bluebirds out of the boxes, and just added a few feathers to the bluebirds nests.  But mostly they didn't have much luck taking nests away from the bluebirds.  If you didn't see it, check out my blog on the house wars I photographed.

This box was started by mountain bluebirds, then four tree swallows displaced them.

Female tree swallows frequently sit in the nest box like this before they have even built a nest and also while they are just laying eggs. This one just snuck into a box used by mountain bluebirds and ultimately kept it.

But while the mountain bluebirds are all almost finished with their first clutches, the tree swallows are just settling down for nesting. The first two earliest nesters each had one-day-old nestlings on my last check, almost a week ago.  The rest are still either building a nest or laying their clutch.  I have seen bigger clutches then I remember from last year - there have been a couple of nests with eight eggs in them.  Imagine having to find food for eight babies!

Only the female builds the nest but the male is usually very attentive

Tree Swallows often have nest attendants. At the beginning of the season, I sometimes saw four tree swallows flying around one nest and tormenting the bluebirds. I was interested to know if these attendants were helpers and would bring food to the nestlings. Apparently they do not, but rather steal food from the nestlings, if they can, according to one paper I found. But they do help intimidate the bluebirds.

The females are sometimes in the box while egg laying is going on but don't start incubating until the next to last egg is laid.  And sometimes, if the weather turns cold, they postpone incubation a little longer.

Tree swallows do return to the same nests year after year.  Last year, when I was entering my data, I noticed that some boxes are traditionally either bluebird boxes or tree swallow boxes while others seem to switch back and forth. I'm certain that the occupants of my box 19E are the same birds that were there last year because they built a super beautiful nest both years and laid their eggs early and had babies earlier than most other swallows did.

Both parents develop brood patches and help incubate the young.  The birds catch most of their prey on the wing - and most is really small, including flies, leafhoppers, bees, wasps, and dragonflies and beetles. . They pack 19 to 34 of these tiny insects into a bolus which is about the size of a BB. One nestling gets one bolus. Since they catch most of their prey on the wing, they  may not be able to find food if the weather turns cold and wet.

The eggs can be white like these or pink like the one in the previous picture. A clutch usually consists of 4 - 6 eggs but a few of my boxes have eight eggs.

Hatch day with one baby showing. I didn't try to count babies this time. 

Hatch day at box 19E last Thursday- how many babies can you count?

These birds are about nine days old - taken last year. 

Tree swallows usually fledge between days 19 and 22, depending on how well they were fed during the nesting period. They have non-iridescent feathers for a few months after they fledge, then start to look like their parents, but with more brown.  I usually don't get to see much of them after they fledge. 

On the personal front, I am getting to go out with Jim and check on water and work on fences. Very fun and gets me into places I can't get in a car.  We were in a mule today.  I'm also spending time entering data from field cameras that are measuring the height of water upstream and downstream of beaver dams.  We'll correlate that with the success of grayling to get upstream over them.  That is not as much fun.  

I'm also trying to finish getting my garden planted and have seeds and seedlings all over the place, waiting to get into the ground.  But my latest garden patch now has 12 wheelbarrow loads of dirt taken from dredging a  boat put-in from lower lake plus composted horse manure mixed with dirt, so it should grow some big plants. 

And we are winding up to have the Rally in the Valley with at least 40 off-refuge adults and accompanying children and dogs. This is in addition to maybe 25 - 30 on refuge adults. We'll be partying Friday and Saturday. I  also will have a friend arriving soon after this blog publishes.  It's going to be a wild weekend here.

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