My website includes a compilation of
information on passive and active means to manage
House Sparrow (HOSP) populations to enable bluebirds to survive
and thrive. It also contains anecdotal accounts of the threat that
HOSP can pose to native birds. Does this mean that I think HOSP
are bad or even evil?
It is tempting to anthropomorphize (acribe human characteristics to) animals. In an attempt to
understand them, we draw parallels between animals and humans.
They provoke emotional responses in us. People may experience anger, horror, disgust, anxiety,
disappointment and/or sadness upon witnessing the results of a HOSP
attack. This can motivate a desire to take action or retaliate.
In part to justify our actions and assuage guilt or discomfort,
or even to feel morally superior, we may tend to demonize HOSP
as vicious or spiteful "murderers."
There is debate on whether animals experience what we call emotions
such as anger. (94% of pet owners think they experience emotions, according to a
2004 survey by the American Animal Hospital Association.) We do
know that different species display different behaviors. This behavior
may be genetically selected for (like a built in "behavioral template"),
enabling one species or strain to survive.
An example is the territorial or possessive behavior
exhibited by birds such as the House Sparrow and House Wren. Both
these species commonly attack the nests and eggs of other cavity-nesting birds. HOSP will also attack adults, perhaps out of an instinctive
drive to reduce competition for nesting sites or food. Supporting
evidence for this theory would be instances where HOSP drive other
birds away from a nestbox, even though the HOSP already have an
existing nest nearby, or when they then do not choose to occupy
the box they have "liberated."
However, HOSP, which are communal birds, do not typically attack each others nests, although they may kill another HOSP when confined together in a trap. Female HOSP usurping the nest of another HOSP regularly commit infanticide (Veiga, 2004). Unlike birds like bluejays that actually eat eggs and nestlings, HOSP aggression is not directly motivated by pursuit of food.
Scientists (e.g., Moyer, 1968 and Paul Brain, 1979) have identified
other types and motivations for aggression, such as:
predatory aggression (induced by stimuli instead of hunger)
inter-male/dominance/social aggression (competition for reproductive success which may be influenced by hormones)
fear-induced or self-defense aggression (e.g., reaction to being confined/cornered)
irritable aggression, and
Not all HOSP will
always behave the same way. Behavior
may be influenced by sex, age, environment, residency, competition, season,
and climate. Individuals have different temperaments
or dispositions. Some individuals or populations are more tenacious
or aggressive than others. Different birds may protect
different size territories. It's possible that reduced HOSP
populations may reduce intra-species competition, resulting
in less-hostile HOSP.
nest in evergreens alongside robins and mourning doves, apparently
without conflict. Keith Kridler reported a pair of bluebirds that successfuly fledged young in a multi-compartment box right next to a House Sparrow nest. There is more visible aggression and possessiveness
associated with nestboxes, possibly because of desirability (protection
from elements etc.), supply and demand, and confined space.
Aggressive behavior can be reinforced
via learning through experience or observation. HOSP are
considered intelligent (in the sense that they can learn
quickly) and adaptable, which has probably aided their proliferation.
Individual birds also occasionally exhibit abnormal behavior which could be associated with what we characterize in humans as mental illness. For example, captive parrots raised in a barren environment may exhibit abnormal behavior such as plucking out all their feathers.
So do I think HOSP are evil? No. The term "evil" generally
implies morally bad, wrong, wicked, or acting out of anger or spite. It is a term applicable to humans.
I do NOT believe that HOSP, either as a species or as individuals,
are "bad" and bluebirds are "good." I believe HOSP behaviors have evolved or are learned as an effective means of self-preservation for individuals and the species. They are doing what comes naturally, and cannot be held to some "humane" human standard. That said, cats are also behaving naturally when they kill birds, but that does not mean I would allow a cat to run loose outdoors and kill wildlife.
I do know that:
Bluebirds are native. Their populations have been seriously impacted by human activity (habitat loss, pesticide use, and introduction of HOSPs and starlings.) HOSP are not native.
Bluebirds' impact on human crops, if any, is
positive as their diet is primarily insects and non-crop fruits.
In part because of sheer numbers, House Sparrows can significantly damage crops,
livestock food and water, etc.
Bluebirds only nest in cavities (natural or nestboxes). HOSP may prefer cavities, but will nest in many other protected places like gutters, signs and evergreens.
Some HOSP may ignore other birds, others may simply harass them to prevent successful nesting, while others will kill.
Aggressive HOSP behavior can cause injury and destruction to native birds. It can significantly impact bluebird survival and reproductive success.
I recognize that some people enjoy HOSP. They are popular birds
in Europe (where bluebirds do not exist.) Some find them clever,
cute, and comical. People appreciate the fact that HOSP are familiar
and friendly towards humans. They enjoy watching HOSP at a birdfeeder
or in a city environment, where they tend to be ubiquitous because
they are so hardy and competitive.
As noted above, in some areas HOSP and native cavity nesters appear to peacefully
coexist. This may be due to a less aggressive population, or HOSP
that have not become accustomed to using nestboxes. I wonder whether
this situation would change when HOSP populations
increase or if HOSP learned to utilize nestboxes which offer
better protection from weather and predators.
In closing, I do not "hate" HOSP, although
I am very concerned about their impact. I try to be objective about HOSP, but I am not dispassionate about conservation.
The bottom line is that I have made a personal choice to help bluebird populations increase. I do not believe HOSP require such assistance. Humans were responsible for
introducing HOSP to this continent. I think it is necessary to try to
restore a degree of balance to the ecosystem which has been upset
by this human intervention. I am motivated by a sense of responsibility
associated with attempting to attract bluebirds to my area. Thus,
I feel compelled to do what I can to protect native birds that
may want to nest in my boxes.
Note: I maintain a small bluebird trail. I am not a psychologist or animal scientist/ethologist. My educational and work background are in the area of environmental science.
The definition of evil: Maimonides (a 12th century thinker) cautioned that our judgement of what quailfies as "evil" is often remarkably self-centered. If something does nto fit our personal desires or interests, we immediately condemn it as evil, as if eveything is all about us.
Weisheit A.S. and Creighton PD, Interference of House Sparrows in Nesting Activities of Barn Swallows, Journal of Field Ornithology, Vol.60, No.3 (Summer, 1989), pp 323-328.
This paper noted that nest destruction can beneift the aggressor if they usurp nests, or have access to more desirable nest sites. Destruction of eggs and nestlings can reduce competitors. But sometimes HOSP apparently enjoy no benefits of interference.
"Life is certainly not just black and white. It is also many shades of gray. (And brown and green and um... blue)!"
- Larry H. Joplin, 2004
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broken links/have suggestions/corrections, please contact me!
The purpose of this site is to share information with anyone interested
in bluebird conservation.
Feel free to link to it (preferred as I update content regularly), or use text from it for personal or educational
purposes, with a link back to http://www.sialis.org or
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