On The Trails: Invasive animals in Juneau

The collared dove is a recent arrival in Juneau and is now seen in many places. (Photo by Bob Armstrong)

By Mary F. Willson

European green crabs have recently been exploding their range in Southeast; they were first officially noted in 2022 in extreme Southeast and are now in Juneau, no doubt on their way north. They arrived on the east coast of North America in the early 1800s, perhaps in ballast waters, and spread their way along the coasts, finally arriving here recently. They have gotten a lot of press, deservedly, because of their potentially devastating effects on natural ecosystems: destroying vegetation and preying on native species.

Reading about the crabs made me think about other invasive animals, particularly birds. We are surrounded by several invasive species of birds, some of which have been in this country so long that lots of folks think of them as native. Here’s a bit of their history and a brief synopsis for our local avian invasives.

Back in the 1800s, it was a popular thing to bring exotic birds to North America, and many people brought over different species, mostly for the songbird trade. Songbirds were favored for their musical abilities and many people kept caged songbirds for that reason.  Some were released but seldom colonized widespread localities or persisted for very long.

Starlings are seen at the landfill and in roving bands around town. (Photo by Bob Armstrong)

One of those birds was the starling, native to Eurasia and Africa, and noted for their musical ability and capacity for mimicry.  A rich businessman imported several shipments of starlings to New York City in the 1800s and his activities were soon followed by others doing the same thing. Not all the introductions were successful, but some of them were and there was a dramatic spread of starlings over North America. Starlings like agricultural fields for foraging and buildings for nest places. These omnivores found lots of food: they are successful scavengers of food not only from agricultural fields, but also livestock feed bins and urban areas; a big flock can clean out a whole crop from a cherry orchard. They have been in Fairbanks since at least 1960; one was spotted in a field in Juneau in 1952. Congregations of starlings in urban areas can make a big, dirty mess of their excrement. A major downside of starling populations is their competition with native cavity-nesters (such as bluebirds and woodpeckers) for nest sites.

House sparrows are relatively recent arrivals in Juneau. (Photo by Bob Armstrong)

Another deliberate introduction was the house “English” sparrow, native to Eurasia.  It was introduced as a pest control agent in an attempt to reduce the vast populations of inchworms in New York. Apparently they were moderately successful at that, and soon other cities acquired their own populations of house sparrows. The birds soon expanded to other habitats, eating crops and so on. Their diet is varied, including human food scraps. They build bulky nests of vegetation, commonly on or in buildings. They were first reported from Southeast in 1987 in Petersburg and established themselves in Ketchikan by 2009, probably arriving in Juneau soon thereafter. In dense urban populations they became annoying to humans because of their rapid reproduction and large numbers, becoming a messy nuisance. 

Rock pigeons or rock doves like city streets and the landfill. (Photo by Bob Armstrong)

Rock pigeons, or rock doves, are native to southern Eurasia and northern Africa. They were introduced to North America in the 1700s or earlier, brought here as human food, messenger carriers, and pets. Most of the ones we see are some of the many domesticated forms of the wild type. These pigeons escaped domesticity and colonized most of North America, including Alaska. Bob Armstrong reported seeing one hitchhiking on a ship from Ketchikan to Juneau in 2013. They eat mostly seeds but have a highly varied diet, including scavenged human food. They often build flimsy stick nests on building ledges and compete with native birds for nest sites and food. They were first recorded in the Anchorage area in the 1960s, but there are reports of sightings in Southeast at least by the 1950s. Miners may have used them as message carriers before that, but the records are not clear. 

Another invasive bird is the Eurasian collared dove. It escaped captivity in the Bahamas in 1974, going to Florida and then spreading rapidly over the U.S. and Mexico. They build skimpy platform nests in trees or on buildings and have a varied diet, mostly seeds. The first record in Southeast is from Ketchikan in 2006 and they have been in Juneau perhaps since about 2016. Their possible effects on native populations seem to be unknown so far.

All of these species can carry diseases that affect other animals, but it is doubtful that they are any worse in general than native birds—except perhaps when they occur in dense concentrations near other animals (livestock, humans, wildlife colonies, etc.). 

Finally, a comment: People sometimes rail against starlings, house sparrows, and pigeons, saying that they HATE those birds. Yes, the invaders can be a messy nuisance, destructive of crops, and so on. However, it is one thing to hate some of what they do and quite another thing to hate a whole species. WE brought them here, and they survived and spread, partly due to their own quite-admirable adaptability and partly with our help. So it seems a bit unfair to hate them in general…the whole species is not really hate-able!

I am very grateful to Bob Armstrong for his extensive, helpful consultation.

• Mary F. Willson is a retired professor of ecology. "On The Trails" appears periodically in the Juneau Independent.