Expert: Roger Lederer - 4/21/2009

Question
QUESTION: HI,
I have been looking all over the internet trying to find an answer to my question with no luck. I am hoping you can help me out. Ok so last year I put up my bird house about 10 feet and had a couple of tree swallows nest in it. (It does face North but that will soon change to East as I have read). My sister lives in the same area and she also had a couple of tree swallows nest in her area. About 10 kilometers out of town my parents had a pair of Tree swallows nest in their house. My parents have always had luck with Barn and tree swallows nesting in the houses and the horse shed and in the quonsite. The past few years they have not had much for barn swallows. Each year they seem to leave after the nests broke and the babies fell from them.
So now last year, we all had these pairs of Tree swallows. We were so excited to watch from afar and have "bug control" in our yards. Well, they all nested in the houses (which they were cleaned from the previous use), they had eggs and were back and forth during the day like we have always seen them do. Then my mom said hers were there one day and gone the next with no trace of babies and nothing! Just gone. My sisters did the same a few days later. Then about a week later the ones in my bird house left.
I am wondering why would they just up and leave?? We want them to stay and feel welcome but don't know why they left?
I cleaned out the nest this spring and found 1 dead baby. It had no feathers on it and I have no other birds around my yard except sea gulls that fly up high cause there is a pond near by and the robins are always flying by. Same for my sister. She has dogs and cats but they could not reach the house. My mom has sparrows and chickadees around the yard. (They stay in the lilacs.) And Robins nesting in the evergreens. She also has dogs and cats who cannot get to the birdhouse.
So after all this we are all hoping that we can attract some tree swallows this year but we are scared to lose them again!
Do you have any idea what might have happened? I really appreciate your time!
Sincerely,
Lacey

ANSWER: Lacey, if I understand you correctly, you are wondering why the Tree Swallows leave as soon as the young can fly? Well, Tree Swallows are very active birds and need to move around to where the insects are. They often fly south as soon as nesting is over. The bird family simply does not stay together as human families do. Once nesting is over and the young leave their nest, it's every bird for his/herself. Thanks for your concern.

---------- FOLLOW-UP ----------

QUESTION: Hi thank you for such a fast replay. We never saw their young as we usually do. It was one day see the parents and the next day they were gone. That is what we are wondering is why they left so fast? There are tonnes of bugs in our area. Also, at my parents house the pair would always stay longer til fall and have a second batch.
Thank you again! :)

Answer
If there were no young, the parents may have abandoned the nest. Could be disturbance, could be predators stalking, could be predators ate one or both of the parents, could be lots of things. Most people have no idea how high the mortality rate is among parents and young  - lots of nests are not finished and lots of young do not survive.