House Sparrow Revenge Syndrome
From: Steven Kroenke, Tallahassee, Florida
We all know house sparrows are mean. But we can make them even meaner. They don't "turn the other cheek"; they get even. We can unknowingly create "vindictive" sparrows.
I studied interspecific competition between purple martins and house sparrows for about 18 years at my Grandparents' martin colony in Havana, Florida. "Way back then", house sparrows were plentiful and tried to take over every martin house/gourd cluster and other bird houses I had erected. It was a constant battle to control them. Fortunately, houses sparrows appear to be on the decline and many martin colonies in my current area of Tallahassee, Florida and in Havana no longer have to deal with them.
I made careful observations and kept detailed records of my observations of behavioral interactions between martins and sparrows. I learned about the physiological and behavioral differences between the two species, particularly how the sparrow's crushing finch beak was far superior to the martin's wide, but weak bill. I also learned that the martin's larger size and aggressive behavior often prevailed over the smaller, but better armed sparrow in battles over nest sites; house sparrows are often intimidated by the martin's larger size and aggressive behavior, particularly early in the season. I learned how the sparrow's tightly built nest was often "martin-proof" and prevented martins from entering house compartments or gourds. I also learned that martins do NOT guard their nests continuously until all the eggs are laid and that sparrows readily entered unguarded martin nests and destroyed incomplete and complete clutches of eggs and built their nest right over the martin's nest. And finally, I learned that simple nest removal will NOT cause a male sparrow to abandon his territory; it just eventually made him meaner and "vindictive". The only effective solutions to house sparrow control were trapping and, when possible, shooting. The sparrows, particularly the males, must be permanently eliminated.
It is important to understand that house sparrows, particularly the males, have an almost unbelievable instinctive drive to procreate. The male house sparrow selects the territory. When their hormones are raging, they go into maximum breeding overdrive and nothing, short of death will deter them from trying to procreate. Also, male sparrows tenaciously hold on to their territory. They do not give up easily.
At first, I used the frequent nest removal method to "control" house sparrows. At that time, I did not have a suitable trapping device and shooting was not always possible. It made no difference how many times I cleaned out the nests as the sparrows would continue to rebuild. The males would NOT abandon the house or gourd cluster. I sometimes waited until the sparrows had eggs and then I cleaned out the nest. Did it work? NO, it did not. But it did do something else.
Remember, the male house sparrow during the breeding season has only one thing on his mind: procreation. So after I had continuously destroyed his nest, he became increasingly "frustrated", aggressive, and began seeking other nest sites within the houses or gourd clusters. Think about this. His present compartment/gourd is not producing young. The site is unproductive. However, he still tenaciously holds on to the "territory" and he still must breed. This territory could include the entire martin house or gourd cluster.
So what does he do? He starts exploring other compartments and gourds for possible nest sites. He starts looking in unguarded martin nests and that is where the trouble begins. He and his mate will readily start building their own "martin-proof" nest over an unguarded martin nest. The martins are often away from their nests for hours until all eggs have been laid, so the sparrows can really pack in the nest material during that time. When the martins return, they will visciously attack and drive the sparrows away temporarily, but the sparrows will be back. All it takes is a few days and the sparrows will have crammed the martin's compartment/gourd full, thereby making it almost impossible for the martins to regain the nest. The house sparrow builds a typical weaver finch nest containing a narrow entrance tunnel that leads to a nest chamber. Such a nest will usually exclude the larger martin from entering. At this point, the martins have lost the battle.
If the martins have started laying eggs, then the sparrows will destroy the eggs and start cramming the compartment/gourd full of nesting material. Though most martins do continuously guard their nests once all the eggs are laid, other martins are not that attentive. The most important role of the male martin during this time is to guard the eggs while his mate leaves to feed; he does not incubate, but serves as a guardian. As long as he is there, the eggs are safe from house sparrows. But I observed many times where males would not remain until their mates returned or would be absent for several hours during the day. Other times, martin pairs were not reliably synchronized in their egg guarding duties. All it took was just a few minutes of unguarded time and a male sparrow could slip in and destroy the eggs.
Here is an example of what a particularly destructive rogue male sparrow did to many of the martin nests in an 18 room wooden house at my Grandparents' old colony site. I had erected the house, along with my gourds and aluminum houses, in mid-January, as the first martins typically arrived in Havana, Florida during the last week of January. Of course, hordes of house sparrows tried to take over and my time was consumed with removing their nests and trying shoot them when I could; I did not have a sparrow trap at that time, but would get one very soon.
The first ASY males began arriving and immediately took possession of their previous sites. As I had observed many times, martins usually prevail over house sparrows at established sites, particularly early in the nesting cycle. The male martins evicted any house sparrows that had taken up residence in the gourds/house compartments where the martins had nested the previous year. The only reason the martins were successful was because I had religiously removed the sparrows' nests so the martins could enter and defend their house compartments/gourds from the inside. But the sparrows did NOT vacate the area, they just moved into empty house compartments/gourds that were not being commandeered by the martins. One thing I did consistently observe was the martins were more successful in out competing sparrows in gourds than in houses. The gourds do not have porches so the sparrows had to battle the martins at close quarters in the gourds; this nearly always favors the martins as sparrows are reluctant to fight larger birds inside the nests. A martin's inter and intraspecific fighting behavior is largely centered in the nest cavity itself. In houses with porches, sparrows can sit on the porches and face martins in head on attacks and have room to maneuver. Martins are no match with sparrows in beak to beak confrontations; the sparrow's vise like beak has far more crushing power than the martin's weak, soft beak.
In the 18 room wooden house, there were 3 house sparrow pairs and all were evicted from their first nest sites by the returning martins. I managed to shoot 2 of the males and their mates abandon the site, but the remaining male sparrow was too cunning and I never could get him. He and his mate selected an empty compartment and started nesting. For weeks I cleaned out their nests and they continued their futile quest to breed. Finally, I let them lay eggs and then removed the nest again. By then there were 10 pairs of martins nesting in the house, 7 ASY and 3 SY pairs and most had complete clutches or were laying eggs.
The sparrows became increasingly "frustrated" and started flying to other sections of the house; they were looking for another more "productive" nest site. They battled with the martins on a number occasions, but the martins successfully repelled the sparrows. During this time, I managed to shoot the female sparrow, but the male was too smart and never allowed me to get close enough. At this point, the male sparrow started a one bird campaign to destroy as many of the martin nests as he could. I remember coming home from school and finding a number of white martin eggs, some with large embryos inside, scattered underneath the house. He had wiped out 2 nests that day. The next morning I saw him fly out of another martin nest with a white egg in his beak. For the next several weeks, that one male sparrow destroyed 8 martin nests and around 50 eggs! He even destroyed the eggs again of 2 pairs that had renested! He seemed to be possessed with a desire to eliminate all martin eggs in the house. I tried to shoot him and by then I had installed a Trio sparrow trap on the martin house pole. He was clever and never went near the trap, though I did catch several other sparrows that had shown an interest in the house. Only 2 pairs of martins in that 18 room house, ones where both male and female faithfully guarded their nests ALL the time, succeeded in raising young.
I experienced similar, though not as extreme, cases of "house sparrow revenge" where I had constantly removed their nests. The sparrows would not abandon the martin colony; they just looked elsewhere in the colony for another house compartment/gourd to continue their quest to procreate. And, unfortunately, many of those compartments/gourds already had an active martin. I was creating "vindictive"and frustrated house sparrows by frequently removing their nests. After these experiences, I still removed the house sparrows' nests, but also trapped and, when I could, shot intruding sparrows.
From my experiences, frequent house sparrow nest removal, without permanent removal of the house sparrows, is NOT a viable house sparrow control method. Such a method may create more aggressive, "vindictive" house sparrows because their nest cycle is broken and yet they still have a powerful desire to procreate. They will just look elsewhere in the martin house/gourd cluster for another nest site to breed. That nest site may just be an active martin nest. Remember: the male house sparrow selects the territory and nothing short of death will usually force to completely abandon the site. He just moves from one house compartment or gourd to another as he tries to set up territory and breed successfully; he will destroy any martin eggs he can. House sparrows must be PERMANENTLY REMOVED from the martin colony.