The more I study birds, the more birds I see headed for decline around the world.
While we get many migrant birds, their numbers seem to be lessening. I really hope the worldwide sparrow disappearance gets solved for the sake of birds everywhere. The study into sparrows exposes a number of causes of decline in many species of bird. Check out the studies…
World Sparrow Day, was on March 20th, the day is set aside to raise awareness about the decline of the House Sparrow, Passer domesticus.
On this day the world over, people exchange conservation ideas which could lead to a better understanding of the worldwide sparrow loss. Finding the cause might protect other birds in the future from the same or similar fate.
Some have expressed extreme dislike for this particular bird. In fact, many look at House Sparrows (HOSP) as worthless, bothersome and damaging. There is certainly no shortage of reasons why either.
- The HOSPs can attack and kill bluebirds.
- They might destroy eggs and young too.
- Native birds like Chickadees abandon nest boxes simply by being harassed by the HOSP.
- A HOSP flock near nest boxes can cause premature fledging of other songbirds.
- They damage crops, and create unsanitary conditions for grain storage.
- They can spread disease like any bird.
- They can overwhelm bird feeders by driving other species away, but I don’t find that here as a rule.
They do many things that makes humans wish for their demise, unfortunately. There are many less sparrowcidal theories as to why they are disappearing though. Let’s see how these studies can give clues for birds everywhere…
One study has proposed that urban noise could be blamed on affecting the parent birds’ ability to communicate with its young. This correlates how often the chicks will be fed. The findings did show that birds living in quiet areas were fed more than those in noisier environments.
It made a connection with fledgling size and even birds making it to that stage. They made note of underweight and undersized birds. Would this not effect all city nesting birds though?
Sparrows like city gardens.
Another study revealed that House Sparrows prefer gardens even over park green space in urban environments. This is because gardens have shrubby cover, while the majority of parks have more open area for recreation for people. The sparrows also like our feeders.
But as seen above, this preferred city living is actually detrimental to the HOSPs raising young due to noise.
Another reason is there are fewer insects needed for the young in urban environments. Urban predators such as feral cats prove detrimental. Cats, both domesticated and feral, kill millions of birds per year.
Speaking of Insects – Insect decline is very telling.
With a warming Earth, cities are getting hotter too. Studies have shown plants are ranging northward in our country due to increased temperatures, but not the insects that feed on them at the same rate. They do not coincide in this slow migration. Warming introduces new plant species to existing habitats, and throws out of sync the eat or be eaten scenario. Plants can become invasive if acclimating to new areas where previously not found. This has happened to the house sparrow coming from Europen to the US.
Some studies postulate that newly invasive species will be winning the battle of survival against the native plants for the simple reason of taste. The native plants will be muscled out by plants not having predators consume them. Less native plants – equals less native insects – which equals less birds that feed on them.
Here is the State of Birds 2010 Report of Climate Change. It is a downloadable PDF.
Since urban areas are so heavily paved, there is little space for native plants to grow, and those that do, get treated for removal in many cities. This is to reduce rodents and insects, and to keep circulation routes visibly clear and safe.
House Sparrows prefer to nest in, on, or near our buildings which is a reason they populate cities. So where does this food shortage for young birds leave the sparrows or any other songbird for that matter?
Plant gardeners, plant.
It is up to property owners to plant to create pesticide free habitats for all birds and the insects they feed their young, and hope that nature resolves the problems of which it is faced. Thoughtful landscaping is all any homeowner can do to help nature help itself.
Large property owners can leave a portion untouched in a natural state, maybe adding more understory plants at the perimeter to woodlands and meadows. They can plant hedgerows for nesting and winter shelter. Many species of birds will benefit.
Pesticides and cell phones?
The HOSP’s alarming decline has been blamed on everything from gardeners’ pesticide use to mobile phone towers. These two theories seem plausible as contributing factors, but again, would be a detriment to all birds.
What’s eating sparrows?
Other reports claim that birds of prey are to blame for the 65 per cent fall in Britain’s sparrows since the 1970s. They cite sparrowhawks and magpies as two birds killing off sparrows. This one seems a bit questionable, even with an increase in raptors after the ban of DDT.
So they did a study with fake predators.
They artificially tested sparrows with recorded predator sounds to come to a conclusion. The “mere threat of a predator to sparrows being exposed to predator sounds has sparrows literally scared into decline” was the theory. They did find that the tested sparrows spent more time in safe places (hiding), consumed less food (by venturing out less), and decreased offspring production (by not searching for mates).
Surprising? I think not. They had the sparrows scared to live normally. But wouldn’t all birds fear the same predation?
Poor planning and use of our urban environments, such as the increase of urban structures, scarcity of street trees, air pollution from vehicular travel, and temperature increases from excess paving, all play into bird loss in general. Again, no surprise.
How about the top 20 birds in decline? Three New World Sparrows made the list.
Drug them out of existence.
I believe many of the noted factors play into the decline of the sparrow, but I am also suspect of the drug DiazaCon that was once used to curb reproduction in the bird and help reduce populations in cities.
“Diazacon was later studied as a reproductive inhibitor for use in control of pest birds. It was thought that since eggs contain cholesterol, lowering cholesterol might inhibit reproduction. More importantly, 20,25 diazacholesterol may have the ability to block production of hormones necessary for reproduction such as estrogen, progesterone, and testosterone. Tests showed 20,25 diazacosterol to be effective in reducing reproduction in pigeons, blackbirds, starlings, and sparrows.” (source)
Likely, there are many causes for decline, but just as likely there is a major catalyst for the spiral downward. One has to question this because, like the study on predation, population decline would be affecting more species of songbird if blamed solely on environmental triggers or conditions. There has to be something specific or endemic to the House Sparrow that is being overlooked or missed.
Are you scared for birds in decline?
Humans take creatures like the sparrow for granted, maligned beings we deem as a nuisance, critters we try to eliminate, birds that have bounty on their heads. Will we appreciate them when they are gone or appreciate that they are gone?