Wintertime Nest Box Monitoring

By Steve Garr, MOBS President

Have you checked your nest boxes since removing the last nesting material of the season? If not, there are plenty of reasons to do so. At the top of my list: to keep House Sparrows from taking up residence in the boxes in the winter.

Most of us who have been bluebirding and raising other native birds in our nest boxes for any length of time have had the great pleasure of knowing some of our boxes will often be used by bluebirds in colder months to roost in at night and stay warm. While I have seen a dozen or more Bluebirds pile into one nest box at night, friends have described scenes in their yards of 20 or more bluebirds roosting in nest boxes. Most information regarding House Sparrows using nest boxes to roost in the winter indicate there is seldom more than one bird per box. This has been my observation as well. This observation might lead some folks to the opinion that since it is “only one House Sparrow” it doesn’t really make much difference to let it stay. I could not disagree more. For starters, that one non-native House Sparrow is taking winter shelter from other native birds (and in the case of bluebirds possibly several native birds at once). But equally as important is the degree to which a House Sparrow will “bond” to a nest box, even in winter, causing it to defend the box even more rigorously in the spring. Basically, we are empowering our bluebird’s competition when we allow House Sparrows to over-winter in our nest boxes. Naturally, we don’t want to do that after making so many good efforts to assist the bluebirds.

In many parts of North America this issue of House Sparrows claiming boxes in the off-season could be of particular importance this year. So many areas experienced a mild and even rather warm Fall. In the area of Missouri in which I live, I believe very warm , summer-like weather contributed to the fact that House Sparrows began putting nest material in my nest boxes in Fall and even as recently as mid December. A recent check of four nest boxes in my small yard produced three House Sparrow nest starts. House Sparrows had also attempted to nest in boxes on my trails- boxes which I had cleaned out for the season after bluebirds had successfully nested this past season. So, again, if you have not looked inside your nest boxes since removing the final nest material from last year, I strongly suggest you do so. And then continue to monitor your nest boxes throughout the winter months. What to do in the event you find a House Sparrow already committed to one of your boxes? I have some tips.

Steps to discouraging House Sparrows from residing in nest boxes in winter:
1. Simply disturbing the bird in the box during the night is a great start. It may be several days before this bird returns. Birds have a tendency to continue to roost in location where they feel safe, so by disturbing them in the middle of the night they no longer feel safe and that location becomes a dangerous location.
2. Place a live-trap in the nest box in the afternoon if you have observed a House sparrow at the box. Place a small piece of grass over the entrance hole to use as an indicator to whether or not a bird has entered the box.
(“Wintertime Monitoring” continued from page 2) Check the box every 30 minutes for bird activity. Remove the trap after your final check for the night and do not leave the trap inside the box over night.
3. If you believe a House Sparrow has roosted in a nest box for the evening, place a clear plastic bag over the entire nest box or over the entrance hole. (Do this after sunset). Tap on the side of the box to try to get the bird to exit the box into the bag. Sometimes you have to partially open the door and slide a small stick around the inside of the nest box to encourage the bird to exit the nest box into the bag. A clear bag is recommended so you can identify the bird in case a native bird had taken over the nest box.

Each year I get inquiries about Bluebirds and Purple Martins. Sometimes the questions may be concerning why folks are getting less Bluebirds each year and more House Sparrows. Or, “Why aren’t my Purple Martins keeping the House Sparrows away from their martin house?”. The answer is the same for both the Bluebirds and the Purple Martins. When a non-native bird that is more aggressive and is determined to kill (not to just chase) the native bird away from the cavity, the more aggressive bird usually wins. Bluebirds and Purple Martins need our help to defeat the House Sparrow. One way we can get a head start on helping our native birds during nesting season is to keep their nest sites free of House Sparrows now.

Take time to help you bluebirds.
Steve

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