A Bunch of Bulbul: Invasive Species on Oahu

Yes, you can think of this blog post as being a bunch of bulbul, because it has pictures of not one, but two species of Bulbul, an invasive species that arrived illegally on Oahu in the 1950s, and quickly established itself as an agricultural pest. It has not managed to spread to the other Hawaiian Islands yet, although a few individuals have been sighted on Molokai and the Kona Coast of the Big Island. The two species are the Red-whiskered Bulbul (Pycnonotus jocosus), and the Red-vented Bulbul (Pycnonotus cafer). I think the bird in the picture above is a juvenile Red-vented Bulbul. It's the only good picture I've managed over the years, taken at Waimea Valley in 2010.

The rest of the pictures are from my most recent trip, and are also from Waimea Valley on Oahu. Above and below are some shots of the Red-whiskered Bulbul, while the last shot below is a Red-vented variety.

So on an island where most of the birds are non-native species, why does this one stand out as a pest and a dangerous invasive species? The state of Hawai'i gives three reasons: They are pests of agriculture and gardens, feeding on fruits, vegetables, flower buds, and insects; they spread the seeds of invasive plants, including miconia, ivy gourd and false kava; and they aggressively chase other birds and compete with them for food and space. There is concern that they may compete with native birds where they co-exist. The Red-vented Bulbul has actually achieved the dubious distinction as being one of the World's Worst Invasive Alien Species.

Let's hope they stay put...

Spotted Dove in Waimea Valley on Oahu

In my other life as a geologist, we have a long-standing adage that you may spend an entire season collecting samples in your study area, and finding at the end that you have not collected a single specimen of the most common rock. That happens with birds too, I have found, and the picture above sort of proves it. It's pretty much the only decent shot I got of a Spotted Dove (Streptopelia chinensis) during my recent journey to the Hawaiian Islands (and of my previous 6 visits as well).

It's not for lack of trying. Upon arriving at the islands we had a three hour layover in Honolulu, and bored, I tried photographing the Spotted Doves running around the airport waiting areas. No dice. They never stopped moving. It wasn't until our last day at Waimea Canyon on Oahu that I finally found one that was still enough for a half-decent shot.

The Spotted Dove has been on the islands for a long time in human terms. They arrived in the 1850s from China, possibly as a food source for Chinese laborers. Some escaped and quickly spread to all of the main islands. Unfortunately they may have been the vector for the bird malaria that wiped out so many of the native species. They also seem to have aided in the spread of the invasive lantana plant. The damage was done long ago however, and since they are mostly found in urban areas, they don't seem to have much of an impact on the remaining native ecosystem.

Zebra Doves in Waimea Valley, Oahu

If you travel to Oahu in the Hawaiian Islands, there are certain birds you will absolutely see. There are the European Sparrows and House Finches that I also see at home all the time. Then there are the Spotted Doves and Myna Birds, which I never see back home. But probably the most common will be the Zebra Dove (Geopelia striata), which seem to be everywhere, starting with the airport lounge and baggage pickup areas (parts of Hawaiian airports don't have doors or walls due to the nice climate).

As I have mentioned previously, the birds are quite polite as a rule, hanging around for food that might drop, but aren't pushy (in my experience anyway; I have heard they'll land on tables). The doves are native to Malay Peninsula, the Philippine Islands, and Indonesia. As adept island colonizers, they didn't take long to spread to the other Hawaiian Islands after they were introduced in 1922.

It's odd, but despite the ubiquitous nature of these little doves, I've had only fair luck in photographing them. They can be very active, and sometimes I miss opportunities because in being so common, I ignore them. In any case, I got these up close and personal shots during our visit to Waimea Valley on Oahu on our last full day in the islands. Waimea used to be a high adventure amusement park kind of place, but is now maintained as a botanical garden (with a dandy waterfall and swimming hole at the upstream end).

Cattle Egret in Downtown Honolulu

I'm back from another long trip, this time across the Pacific Northwest, and Wi-Fi was hard to come by in the wilds we were exploring. But now I can continue our exploration of the birds of Hawai'i, and then move on to the Pacific Northwest species I was able to photograph during the last two weeks. Today's species is the Cattle Egret (Bubulcus ibis) that I was able to shoot while strolling through a coastal park in downtown Honolulu.

The Cattle Egrets have an uncomfortable history with Hawai'i. They originated in Africa, spread to north and south America, and were introduced for pest control purposes in Hawai'i in 1959. They did their job, inhabiting pastures and fields, picking off flies and other biting pests. But as agriculture has decreased, and interest in preserving the native species increases, the Cattle Egrets have become a problem, as they compete for food resources, and pick off the eggs and chicks of native species on the islands, especially the Stilts and Coots.

Red-crested Cardinals on Oahu

In 1928 or so, the coastal towns and farmlands of Hawai'i were bereft of native bird species. Non-native species brought to the islands for a number of reasons had carried in their blood the parasite that caused avian malaria. Mosquitos transferred the disease to the native birds, and they were largely extirpated from the coastal lowlands. Most of the natives only survive above 4,000 feet where it is too cold for the mosquitos to thrive.

It wasn't that there were no birds at all in the lowlands. The Common Myna, introduced in the 1850s to control pests in the sugar cane fields, was...uh...common. There were also Spotted Doves, House Finches, and European Sparrows. But these weren't enough for some of the residents. In the 1930s, a bird club called Hui Manu devoted itself to introducing colorful and interesting birds to the islands. The effort was well-meaning, but misguided as one could imagine. Some of their introductions spread well beyond the coastal forests and spread into the higher forests where the native birds struggled to hang on. The new competition didn't help matters.

In any case, a number of the introduced birds were naturalized, and have spread widely. These are the birds most likely to be seen by tourists who stay in the coastal cities. And some of them are very colorful, literally a delight to the eye. Among them most be counted the Red-crested Cardinals (Paroaria coronata). The red head and crest seem to throw off the color balance on my camera sometimes. I saw them all over Oahu, but got the closest when we visited Waimea Valley on the North Shore, and at Kualoa Regional Park west of Kailua. Kualoa is one of the most beautiful shorelines on Oahu.

The Red-crested Cardinals rarely venture above 1,200 feet, so they probably can't be regarded as one of the "bad" invasive species that threaten the livelihood of the native species of Hawai'i. They certainly add a splash of color to the urban and developed areas of the islands.

And Here's the Grown-up Shama Thrush at Waimea Valley

The Shama Thrush (Copsychus malabaricus) is native to southeast Asia, but was introduced into the Hawaiian Islands in the 1930s-1940s. It has spread widely through the coastal forests of Oahu and Kauai, and would have competed against the native species, except that the natives had been extirpated by avian malaria and lost habitat. Some of them have in fact spread into the higher altitude forests where they may cause problems for the natives.

Thus it is that I have ambivalent feelings about the non-natives. I deplore the destruction of the original habitat and the loss of so many native species, but I also couldn't wish for the silent forests that led some well-meaning people to release their caged birds as a way of repopulating the coastal forests of Hawai'i. And certainly many of the new birds are colorful and interesting.

We saw this male Shama Thrush while we strolled through Waimea Valley on the North Shore of Oahu (we saw the juvenile and a female in yesterday's post). Like the bird, Waimea Valley is not exactly natural either. It's a botanical garden, filled with plants from all over the world. In an odd way, that makes the presence of the Shama Thrush a little less out of place. In any case, it is a beautiful sight.

Juvenile Shama Thrush in Waimea Valley on Oahu

A visit to the Hawaiian Islands for birding-type people can be an exercise in frustration. Hawai'i is well-known as an example of evolution in action: isolated islands that were colonized thousands or millions of years ago, producing myriads of new and fascinating species, including birds. For instance, the honeycreepers, small finch-type birds, diverged into at least four dozen new species. Most are extinct, but some are left, and finding them can make or break a trip, depending on how focused your goals are. The problem is that mosquitoes were introduced to the islands in the early 1820s, and they brought avian malaria. The disease wiped out the native birds in the coastal areas. The species that survived found refuge in the forests above 4,000 feet, where it is too cold for the mosquitoes to thrive, but the coastal forests became silent.

Invasive species were introduced for a variety of reasons. In some cases, such as with the Myna Birds, they were brought as a method of controlling pests in the sugar cane fields. In others, caged birds escaped from their owners. In at least one case that I heard of, a pet shop went bankrupt, and the owner simply let all of his birds go. There were even well-meaning people who released birds on purpose to repopulate the coastal forests with songbirds. Overall, these new species put even more pressure on the natives, as they often competed for the same food sources.

So birding on the islands is a mixed bag. As a rule, one will not see native species unless a special effort is made to visit their habitats. And yet, the invasive birds are often quite beautiful speciess that have become naturalized in their new habitat. They are colorful and are often easy to photograph in heavily visited tourist areas. As such, they'll be the focus of my next few posts. While we were on Oahu, we made sure to get out of Honolulu and explore the wilder parts of the island, including the Waimea Valley on the North Shore.

Waimea Valley is not exactly a native Hawaiian habitat. It was once an adventure park that has since been converted into a botanical garden with species from all over the world.  It therefore almost makes sense that exotic bird species would be common here as well. As we walked down the pathway, I saw an unfamiliar bird on the basalt boulders and got some pictures. I was starting to thumbing through the bird guide to identify it when I realized it was a juvenile, mainly because momma showed up to feed the hungry teenager. It was a Shama Thrush (Copsychus malabaricus), sometimes called the White-rumped Shama. It's a native of Asia that was introduced in the 1940s. The guidebookss share the collective opinion that it has one of the finest songs on the islands.

There were male Shamas in the park too. They'll be in the next post.