Today I get serious about the attack of house sparrows that I have on my bluebird boxes and Purple Martin house. Again, this morning I tore out a house sparrow nest in my Purple Martin house. That house sparrow is rebuilding that nest as I type this. One of the bluebird boxes has two house sparrow eggs in it. I was going to toss the nest out with the eggs but thought there might be a better way. I checked the Internet and found out there is several ways to deal with a house sparrow infestation. Some good and effective and some not so good nor effective.
I have already found one bluebird egg pierced and destroyed. The bluebirds have since laid five more eggs and they are guarded by the biggest bluebird I've ever seen. Last year three Purple Martin nestlings were pecked to death by the house sparrows trying to take over their nest. This year three of the apartments have Purple Martins in it but I haven't checked to see what their status is. I'm trying not to disturb them. I also have a gourd that swallows are nesting in.
I checked all the methods for controlling an infestation of house sparrows and the best one seems to be oiling the eggs, thus preventing air from getting to the embryo. Other options are freezing the eggs and putting them back in the nest. Piercing the eggs but you have to be careful to pierce the egg thoroughly or else you'll have the birth of a deformed sparrow. I don't want to cause any more harm than necessary. What I do want to do is provide a safe and secure environment for my native nesting birds to have a place to raise their young.
Tearing out the nests and eggs apparently doesn't stop the house sparrow from building another nest. The best thing to to is to keep the little buggers occupied with their eggs. Thus oiling the eggs seems to be the best option at this time.
I've posted a picture of what an aggressive house sparrow does to a bluebird when they want their nesting site. It is not a pretty picture. As much as I hate to destroy a bird nesting site, it is necessary if we are to maintain at least some of our native bird species such as the bluebird and Purple Martin.