I have a House Sparrow "condo" on an 8-foot pole about 20 feet from the
dining room window. The condo has 4 floors and 5 rooms. The third floor is
split into 2 rooms.



I also have a remote temperature device I got from Radio Shack. It has an
indoor receiver that reads temperatures from three remote sensors. One of
the sensors is attached to a tree a few feet from the sparrow condo. When I
originally installed the condo a couple years ago, I put temperature sensors
in each of the two third-floor rooms. I put a piece of window screen over
one of the entry holes to the third floor rooms as a control. The idea was
to see if I could tell when the unscreened room was occupied by the
temperature in the room. It works (although the "control" turned out to be
a poor control for a couple of reasons I won't go into). At night, the
occupied room is a few degrees warmer than the unoccupied room, which is
usually a little warmer than the sensor in the open. At the end of the
breeding season this year, I removed the screen, so the birds can now use
all the rooms.



The sparrows use the condo nearly year-round, with a short break between the
end of the breeding season and the onset of cold weather. The flock seems
to have about 16 members as of my last good count, down from a brief high
this year of about 25. In winter, the sparrows usually leave the condo just
before dawn very quietly and inconspicuously. They revisit the box at least
once, often around midday, in a noisy, chirpy bunch, sometimes briefly
entering a room. (Deciding where to spend the night and checking to make
sure the accommodations are still available?) In the evening, they enter
the condo for the night as the sky is graying. This time of year, usually
between about 3:40 pm and 3:50 pm. They are usually fairly quiet as they
retire and zip in without much fanfare. I miss the event if I don't watch
closely.



Social animals are always balancing the benefits and drawbacks of
sociability. It's important to get along with the group from which the
individual derives much benefit, but the members of your own species,
including the members of your group, are also competing for the same
resource. In this case, the resource is a warm place to spend the night,
which can mean the difference between surviving the night or being a
sparrowsicle in the morning. As the weather has gotten colder, the sparrows
have been having more quarrels about who gets to sleep where. With this
current onslaught of bitter cold, finding a sheltered place to spend the
night is critical.



Monday evening at sparrow bedtime, I saw about ten of the sparrows perched
in a small leafless tree next to the condo. A few more sparrows were
already in the condo. From what I can tell, sparrows are picky about their
nighttime companions. Since they sometimes enter and leave multiple times
before settling in, I'm not sure how many sparrows typically occupy each
room, but it appears to be only two. Often, a sparrow will hang at the
entrance to a room looking in, then fly away when the sparrow already inside
pecks at it. Then a different sparrow will fly up and enter without
hesitation. Since there are only five rooms, some of the sparrows get left
out. They have to spend the night in the shrubs (some type of ornamental
arborvitae, I think) next to the house. Monday, the jockeying for rooms in
the condo continued for about 20 minutes, as if the sparrows realized that
the cold was coming. Tonight, they entered with their usual quiet alacrity,
having evidently fine-tuned the sleeping arrangements the night before. I
startled a sparrow from a shrub when I opened the back door after dark, so I
know not all of them found a room at the inn.



When I last checked the temperatures, the sensor in the open was 13 F, the
sensor in the sparrow room that was never screened was 18 F, and the sensor
in the formerly screened room was 16 F. (The formerly screened room
doesn't have any nest material since it was blocked until recently, so the
sparrows have less insulation.) It doesn't seem like a large difference,
but it's amazing that a couple of tiny sparrows can generate enough heat to
warm a relatively large sensor several degrees. The condo also, of course,
protects them from the wind and from radiative heat loss to an open sky.



Reminds me of how nice it is to spend the winter in a heated house.


Kelly Cassidy