Saturday, May 1, 2010

Invasive Nest Building

When I first started bird watching, I treated all birds the same. My earlier blog posts would reveal this, I'm ashamed to admit. Back then, it didn't matter if they were Golden-crowned Sparrows, Downy Woodpeckers, Northern Flickers, or House Sparrows...I loved them all the same.

Well, things have changed.

After spending time out at the George C. Reifel Migratory Bird Sanctuary on Westham Island, I've watched as Tree Swallows were evicted from Nesting Boxes by aggressive invasive species...left, right, and center. The invasive species I refer to are House Sparrows...the most widely distributed wild bird of all. For more information on the House Sparrow, visit The Cornell Lab of Ornithology "All About Birds"

Here are a series of photographs I took, shortly after a Tree Swallow left her nesting box in search of food....

After a short while, the Tree Swallows returned. They tried, in vain, to chase away the House Sparrows. All they could do is sit in a nearby tree, devising their next plan of attack...

Tree Swallows are forced to be vigilant. Often, one of a pair would remain at the nesting box, while the other left in search of food. Once one returned, the other would depart.

Which would you prefer to see nesting?


  1. The most ironic thing is house sparrows are declining here in the UK, where these ones probably originated...

  2. Really? Do you know why they're declining in the UK? Is it lack of habitat? They nest just about anywhere there is a manmade structure, whether it be in the eves or on the back of street lights.

    I'm gonna "google" that! Thanks for your comment.

  3. Interesting information HERE regarding the decline of the House Sparrow in the UK:

  4. What a fabulous post :) I love this !!
    Hope you will show us the whole family soon ;))

  5. Interesting post Kim, I still like the house but it is sad to see. they have started nesting in purple martin box at milford ct too, hopefully the martins will chase them out


  6. My Mother, back on our Saskatchewan farm in the 1950's, never fired a gun in her life, until house sparrows molested the bluebirds nesting in the box on our clothesline pole. She picked up the family .22 rifle and blew the male into a ball of blood and fluff.

  7. Umm, wow Ken. That's a bit extreme but I guess solves the problem for the short term.

  8. I didn't notice the word "non-native" in this excellent post. Lots of organisms are "aggressive," but it becomes a problem only when they are introduced species, which House Sparrows are in North America. I've been impressed, too, by their abundance in the swallow boxes at Reifel; there's no reason, legal or moral, not to remove those introduced birds and to give the native species a break.

  9. Invasive is right! My H. Sparrows are already feeding their fledglings at the feeder. It's been nice having a break from them while they were nesting.