Invasion of the bulbuls: Houston team studies new invasive species

Editor’s note: This blog post is a summation of “Ecology, Behavior, and Reproduction of an Introduced Population of Red-vented Bulbuls (Pycnontus cafer) in Houston, Texas,” written by HMNS Curator of Vertebrate Zoology Daniel M. Brooks and published in The Wilson Journal of Ornithology.

 

Invasive species are (unfortunately) nothing new to Texas. Defined as an “introduced species that adversely affect the habitats and bioregions they invade economically, environmentally, and/or ecologically,” invasive species (aka invasive exotics or exotics) can have wide-ranging negative impacts on regions.

Species such as giant salvinia, feral hogs, zebra mussels and nutria constitute invasive species currently wreaking havoc on Texas wildlife, having decimated food sources and changing ecological dynamics, and even threatening other species’ survival in their environmental niches. It’s for this reason that many scientists have begun to study introduced species and their behaviors before they decimate their new habitats.

In light of this, Brooks initiated the Texas Invasive Bird Project in June 2008, a citizen-science study targeting six avian species invading the state. One of these is the red-vented bulbul (Pycnonotus cafer). This species was previously unstudied in Houston.

The red-vented bulbul is native to Pakistan, India, and Sri Lanka, but has become a well-established invasive species in parts of the Middle East, various tropical Pacific islands … and Houston. In its native and introduced regions, it can be found in a variety of habitats, including urban gardens. In the Houston study, we aimed to determine the ecology, behavior and reproduction of the bulbul through a questionnaire made available at birdwatching clubs, annual birdwatching festivals and circulated on internet list serves. Most of the respondents were either birdwatchers familiar with bulbuls or horticulturalists who maintain diverse gardens.

The results determined that the most frequent activities for the birds included foraging, perching or resting and calling. Ninety-six percent of the reports described residential suburbs as the primary habitat of the birds, with the highest concentrations being found in the Heights neighborhood. In these areas, they were observed perching on 35 species of plants, and feeding on 20. Forty-three percent of the plants they perched on are native to Texas, while only five of the 20 plants they fed on are native to Texas. The most common plants used for perching were also exotic plants (bamboo, crepe myrtle, fig and tallow), which are all found in the native range of the bulbul.

They are generally non-migratory birds. But the largest flocks appear at regular intervals between August and September, and then again from December through January, traveling in flocks of 12 to 22 birds. This matches their patterns in other regions, while their numbers are much smaller in Houston (with gatherings of 20 to 100 birds within their native range).

Ultimately, it seems that bulbuls are not currently a threat to Houston, but they should continue to be closely monitored. While they pose no current negative economic threat as they do in Pacific islands (such as Oahu, where they’ve decimated tropical plant crops), it seems that their largest potential threat in Houston remains through seed dispersal. In this area, they have great potential to disperse noxious weedy seeds, as they have done in Fiji with spiked pepper, guava, and prickly night-shade.

In the meantime, the birds seem to be enjoying their niche in previously untapped resources of other exotic plants brought to Houston and used in gardens, which other birds have not used with great regularity to eat or perch in. However, as the population continues to increase and spread through the region, we will have to monitor any changes that may occur which could negatively impact native species.

Searching for Elvis, (Jim, Janice and Jimi)…

So far many of the tales I have told (all true by the way) have dealt with a common underlying theme – life through the eyes of a budding young scientist.  This is because I have hacked away at information from old camp logs and field notes from the early days in my career to bring you, the reader, vivid pictures through these stories.  The next reading is no different except that it takes place not in Latin America, but here in our own backyard, the USA; specifically, southeast Arizona. 

Approximately 15 years ago, while working in a job that involved little variation in day-to-day work, one of my co-workers, Jerry CrabbyOtis (Crabby hereafter) and I would take up the topic of bird-watching (birding), which we both enjoyed thoroughly.  He was much better at birding than I, as he had been doing it for a longer period of time than I. 

One day Crabby returned from a trip to the Chiricahua Mountains of southeast Arizona.  Before leaving for Arizona, Crabby was stressed out, malnourished, and probably had a G-I tract perforated with ulcers.  When he returned only a week or two later, it was like he had been sent to a rapid-advance rehab facility – he was relaxed, bronze-colored from the sun, and full of more excitement than you could shake a stick at!  It was as if he was a Greek leprechaun who had found a pot of gold, returning to report his quarry. 

“DAN – you gotta go to the Chiricahuas man…,” he said, trying to get my attention.  After he described the beautiful northern offshoot of Mexico’s Sierra Madre, and all of the tropical wildlife that thrived there, I decided a trip could well be in order. 

I telephoned a friend, Steve Mayes, who was also doing the daily grind and in need of a fun diversionary field trip.  Steve and I planned our trip to take place later that summer.  We charted all the hot spots for tropical wildlife (especially birds) in southeast Arizona.  This would be a great opportunity to do a little field work and collect scientific data on various topics involving animal foraging.  I had just received my Master’s degree and wanted to take a stab at designing my own experiment, independent of an experienced mentor.

Above all, we joked around about the possibility of finding Elvis Presley, Jim Morrison, Janice Joplin or Jimi Hendrix on a street in Tucson.  These talented musicians, who all met a tragic end, were the subject of urban myths, perpetuating they had moved to Tucson after becoming weary of the daily grind of a famous musician.  We knew the trip would be fun, and after all, someone once said, “Nothing is worth doing unless you are having fun.” 

As evening falls
Creative Commons License photo credit: kretyen

Searching for Elvis, (Jim, Janice and Jimi)…

August 1994
Tucson, Arizona

When we arrived in the late afternoon, worn out and exhausted from the long and grueling drive from Texas, we scouted a bit and pitched camp in this ‘foreign,’ yet beautiful, habitat.  I cautiously prepared the feeding tubes with three different concentrations of sugar water: no sugar in the control, 5% sugar and 20% sugar.  Then proceeded to hang the feeders at the same height and distance from one-another.  I was a little nervous, as this was my first ‘solo flight’ with experimental design. 

Within a few minutes of dusk approaching, several nectar-feeding Long-nosed Bats (Leptonycteris curasoae) began hitting the feeders.  Within a few minutes of that, the bats figured out which feeder was most concentrated with sugar and ignored the other two.  Risk-sensitive foraging in action!  The same pattern was observed the following morning with the hummingbirds, and within a few minutes of that the hummingbirds illustrated extreme size-mediated competition, with the larger species ousting the smaller species from the feeders.  This pattern held for each site we ran the experiment at, all at varying altitudes with a different of hummingbird community.  My experiment worked!! 

Elegant Trogon
Creative Commons License photo credit: dominic sherony

That first morning at Sunny Flats, we set out to see what wildlife we could see in this semi-mesic Oak forest surrounded by low-lying desert.  One of the first birds we saw was one of the primary target species – a female Elegant Trogon (Trogon elegans) feeding her youngster.  Shortly thereafter we saw a mixed flock comprised of three Bridled Titmice (Parus wollweberi), two Yellow Warblers (Dendroica petechia) and a Painted Redstart (Myioborus pictus), with the latter being the alarm-calling sentinel, warning the other birds of our presence.  We even saw a lone male Coati (Nasua narica) on the way back to camp, rooting around in the understory. 

Things like the trogons, coatis, and other Neotropical species we saw are difficult to impossible to view in other regions of the the U.S., so being able to see these tropical species in this region was a genuine thrill!

One of several other sites we visited was a Nature Conservancy property called Ramsey Canyon.  Within a few minutes of leaving the truck, we saw a sow and half grown cub cinnamon-phased Black Bear (Ursus americanus) strolling leisurely at the bottom of a hill, perhaps 100 yards or less from where we stood.  I could feel the hair on the back of my neck stand.  It was Ramsey Canyon where we hoped to see the Eared Quetzal (or Trogon, Euptilotis neoxenus).  After spending several hours hiking up mountainsides into appropriate habitat where we might encounter the bird, we struck out and finally threw in the towel a little before dusk.  We were juiced to continue our long and grueling hike, as we thought (?) we heard vocalizations, which drove us to continue on our quest for this cryptic species.

Black Bears ended up being somewhat common in southeast Arizona.  In fact, we found several piles of fresh bear dung, full of the berries that were in full bloom in the arid mountains of this region.  [At the time, I was very interested in ecological interactions of South American fauna and flora (as I still am today)].  One of the fascinating new findings in South America was that a carnivore, the Maned Wolf (Chrysocyon brachyurus), was actually an important disperser of some of the fruits it preferred to eat.  So naturally, I wanted to see if the Black Bears were dispersers or predators of the berries they consumed.  I had to bring Crabby back some sort of ‘gift’, so I figured, why not some bear feces to do germination experiments with, since he had such green thumbs after all!

Now we’re sitting on a bench in an urban park, catching our breath after playing Frisbee, and getting caught up on the field notes.  We have looked high and low for Band-tailed Pigeons (Patagioenas fasciata) with no luck, despite being the right time of year to catch a glimpse.  Steve was relaxing, contemplating his surroundings, as he often does.  Then he looks over at me calmly, hits my arm to get my attention, and upon doing so just holds his hand with his index finger pointing towards the sky.  Following his directions, I see a resting Band-tailed Pigeon perched just a few feet over our heads.

Post-log (12 January 2009):Well, Crabby’s bear dung never germinated any sprouts of a plant despite his green thumbs, which told us the bears are actually seed predators in this case.  The lesson learned with the Band-tailed Pigeon has again and again provided some of the most obvious answers to some of the most daunting tasks or questions I have encountered in life thus far.  That is, that the answers are often right in front of our faces, if we can just slow down long enough to ‘see’ them.  I have remembered this hilarious moment of the Band-tailed Pigeon perched over our heads, yet have found it to be so true in tackling research questions, dealing with crazy personalities, and other formats of problem solving – the solution is often right in front of you.  Even though we never met up with Elvis, Jim, Janice or Jimi, I could have sworn I caught a fleeting glimpse of one, or the other, out of the corner of my eye on several occasions.

Incidental Herping and Heroes

Southeast Arizona desert

Southeast Arizona desert

I recently took an all-too-short birding trip to Arizona. (Birding is like bird-watching only more sciency.) While my friend Martha and I set our sights on finding some of SE Arizona’s more glamorous birds, we did take the opportunity to check out some of the other local fauna. We were privileged to observe kangaroo rats, a family of javelina, swarms of mosquitoes and a variety of very speedy lizards. Here are a few of the non-blurry pictures we managed to snap of the slower daytime critters.

aponophelma species

Wild tarantula peeking out of her hole at the Sonoran Desert Museum - in the bird aviary!

dung beetle

A dung beetle! If you look closely you can see the ball it is rolling.

western box turtle

Martha first spotted this little cutie on our walk in San Pedro Valley.

While lots of animals are active during the day, some are easier to find at night. Daytime or nighttime, herping is good, clean fun. It’s a lot like birding, except with reptiles and amphibians and more often than not you try to catch them. Herping, especially in the desert, can be very rewarding once the sun sets. As the air cools, the roadways retain a lot of their warmth, which reptiles and amphibians crawl out to absorb.

Summer is also monsoon season in SE Arizona, so toads are just as likely as snakes. Our nocturnal guides on our mini-excursion were none other than the same folks who had rescued us the night before from atop a mountain when our rental had a flat tire and a leaky spare – a story for another time but heroes none the less. Quick shout-out to Nick, Mary, Steve and Becky!

As we set off into the night, watching a spectacular lightning show to boot, Martha and I followed behind our knowledgeable leaders in our car. How prepared were they? They even had these cool radios so when we stopped abruptly I would know where to park without running over our intended “catch”. Of course, we only handled the nonvenomous reptiles and all of them were herded or released to the side of the road. Safety first! Here are some of the pictures Martha took since, wouldn’t you know it, my digital’s batteries died after the first rattlesnake.

great plains toad

One of our first toads: a Great Plains Toad, who it turns out can hold quite a lot of water.

couch's spadefoot

I was surprised at the greenish tint of this Couchs Spadefoot toad.

mojave rattlesnake

All of the rattlesnakes we found at night were juveniles, and none were as large as this Mojave Rattlesnake.

rock rattlesnake

I found this Rock Rattlesnake as we headed to Tucson, though not under a rock.

Threadsnake

I still do not know how Nick spotted this Threadsnake on the side of the road. Now to count the head scales to accurately identify it.

desert variation of common kingsnake

After this gorgeous Desert Kingsnake finished defecating all over Nick, I got to hold it!

longnose snake

One of the more colorful snakes we saw that night, the Longnose snake.

Martha, not necessarily a fan of snakes but more an appreciator of amphibians, was very patient with me when I requested she photograph each of the critters we saw. We had a great time and would have stayed out longer had the weather been slightly more cooperative.

aphonophelma species

aphonophelma species

On our way back to Tucson to catch our flights home we also were lucky enough to spot this little beauty (at 70 mph no less) crossing the road. By the time I turned around we had nearly lost it to the roadside shrubbery full of cows. We had a great adventure and can’t wait to plan another trip to spot all those we missed this go round!