Tag Archives: innovation

Aerial Mist Netting: Necessity is the Mother of Invention

Another crucial skill for field ornithologists is being familiar with mist netting and bird banding. Stringing up mist nets is often the most effective way to capture birds, especially when used in conjunction with audio playback to draw in potential targets. The nets are usually placed between two trees or poles, creating a nearly invisible barrier for unsuspecting birds to fly into. They then become tangled in the finely-woven web, allowing for the biologists to step in and carefully remove them. Birds can be caught in this way for any number of processing procedures, including banding, physical measurements, and collection of blood or feather samples. They can also be turned into specimens.

Our Cardinalid project here in Tompkins County did not specifically require any data from netted birds. Our focus for this season was primarily on behavioral ecology, which can be observed in the bird’s natural setting. However, we still recognized our study site as a great location for learning the basics of mist netting. More importantly, it was imperative that the Borneo crew be well-versed in proper net set-up and bird handling, as much of the information they hoped to obtain in Tawau was dependent on the capture of individual birds. However, there was an additional snag that came along with this need: many of the target Bornean birds live at higher levels in the forest foliage. While mist nets are typically placed on the ground and extend as high as the poles they attach to, a significant number of the target taxa for Tawau are primarily birds of the canopy. As such, we were faced with the challenge of not only refining our basic net and bird handling skills, but also trying to come up with a way to catch higher-flying species.

The answer to this problem turned out to be surprisingly simple, largely thanks to the ingenuity of crew member Justin Hite. Using the tools at our disposal, we were able to design and construct an elegant and efficient means of placing nets at greater heights than usually possible. To begin, a “backbone” of p-cord was strung between two trees at the desired vertical level for the nets to hang from. This was achieved either by throwing the ends of the rope or using the large-size slingshots provided for us by the Cornell Outdoor Education department (COE). Next, full loops of p-cord were then attached to the “backbone” at either end. These loops were large enough to run from the ground up to the line, and they were fastened in such a way that they held their position horizontally while still maintaining the freedom to move in a continuous loop. Lengths of PVC pipe (with holes punched in them for attachment of mist net trammels) were then tied to these loops so they could easily be brought down to ground level or run up to full height. The ends of these loops would be tied to nearby trees to keep the nets taught, but could easily be undone to lower them on command. Once the nets were strung between these pipes, the system was ready for operation.

We set up several “net backbones” at various heights in different locations of interest. Our on-the-spot solution to a very important problem proved more effective than we ever expected. We caught a wide variety of species in our nets over the weeks, including Ovenbirds, titmice, and various thrushes. This allowed us the chance to practice extracting birds from the netting and processing them for data and banding. What’s more, our system was found to be surprisingly efficient even when capturing birds in the treetops. The total time it took from a bird hitting the net to returning the emptied net to position was only about 2 minutes. Mind you, that includes getting to the net, freeing the loops, lowering the PVC pipes and net, extracting the bird and placing it in a bird bag, running the nets back up, tying them off, and returning to the banding station! Not bad for a morning’s worth of crafting.

We can only hope the system we devised has been equally effective for our colleagues in Borneo!

Leave a comment

Filed under Birds

(Un)happy Endings

Even for birds, things sometimes don’t go as planned.  In fact, we’ve found that for Rose-Breasted Grosbeaks, life often doesn’t follow its intended course.  None of the Grosbeak nests we’ve found have lasted until the chicks fledged, and many were “popped” (eaten) or abandoned before the eggs even had a chance to hatch.   After six failures, but before we resigned ourselves to the apparent curse of the Pheucticus, we did a little research.  Friesen, Cadman, and MacKay found that only 46% of the Rose-Breasted Grosbeak nests they kept tabs on made it to completion, i. e. 54% of their nests did not yield any fledglings (1999).  Compared to our 0% success rate, 46% was looking pretty good.  However, Dungay, Woods, and Nichols reported a success rate of only 32% (2001).  Consultation of the Birds of North America account revealed that our Grosbeaks’ low success rate may also be a consequence of the fragmented nature of the available habitat.  Despite their preference for fringe habitats, Rose-Breasted Grosbeaks also tend to have a lower nesting success rate in more fragmented habitats.

Taking all this into account, and pushing valiantly through the heartbreak of losing yet another nest, we decided we needed to make darn sure the nest was empty.  We had assumed the happy Grosbeak couple was incubating when one or the other was constantly on the nest, which we first observed on July 2.  This meant that there should have been eggs in the nest.  To check for the presence of eggs, we used a very special piece of equipment: a nest mirror (also known as a mechanic’s mirror).

The basic plan was as follows:

Much more difficult than anticipated!

Operation Nest Mirror

Simple enough, right?  We thought so.  However, we forgot that the nest, although located relatively close to the ground, was also directly over a giant patch of honeysuckle.  After several tries, Hilary eventually managed to hold the mirror in a position that reflected the image of the tragically empty inside of the nest to Emma and me, who were looking on intently with binoculars and a camera.  Although our hard work revealed nothing but an empty nest, we felt we had accomplished something by figuring out how to look inside a nest that was way above our heads.  Hopefully the next time we use our ingenuity to look in a nest, we’ll be greeted by the sight of happy little chicks!

1 Comment

Filed under Birds

What Could be Better than Ice Cream?

Two Fridays ago, our research team headed into the field, eagerly anticipating the prospect of Purity ice cream at the Lab of Ornithology’s social that afternoon. Little did we know that we were in for a very different (and as much as we love Purity ice cream), even better, treat.

Opening up what we’ve termed our “nest contents” spreadsheet in Excel, we briefly scanned our timeline to gauge the approximate time of hatching for our only active Scarlet Tanager (Piranga olivacea) nest at the time. The Scarlet Tanager account on BNA (the Birds of North America Online) describes departure from the nest on day 9 or 10 after hatching; by our rough calculations, the fledglings at our nest of focus would either be near the nest, already out and begging for food, or in the nest, close to fluttering out. With that in mind, Jen and I decided to head out for a two-hour nest watch, lugging – just in case – the HDV camera lent to our team by Macaulay.

While Eric and Tim went in search of new nests and juveniles, the two of us settled down in a spot where we could get a clear view of the nest (SCTA5 is notorious for being extremely well-hidden). After focusing the video camera on the delicate, saucer-shaped nest far above our heads, we started the watch. The first 30 minutes or so were much like any other day of nest watching involving parental care of nestlings – one parent at a time arrived to the nest at varying time intervals – the only exception, however, was that within that first half hour at SCTA5, only the male visited the nest.

For a brief (and of course, always exciting!) snapshot of our nest watch that day:

At 10:55 AM, as the parents were out foraging, there was some slight movement on the nest.
At 11:01 AM, the male was singing softly as the female called in the under-story, on a branch remarkably close to the observer – both aspects being atypical for the behavior of a female tanager while foraging for her nestlings.
For the next five minutes, the female gradually moved closer and closer to the forest floor directly below the nest, continuously chck-brrring.
At 11:05 AM, sounds that seemed to be begging calls were heard. The male and female continued to sing and call until suddenly, there was a small flash of a fluffy grey bundle scurrying towards a log.

Yes, indeed – it was a Scarlet Tanager fledging, our first one seen straight out of the nest.

The HDV camera Jen and I had luckily brought out was quickly trained on the fledgling, who was remarkably agile. He was able to make his way across the forest floor fairly quickly and was capable of short, fluttery flights. As Jen and I followed him from one log to another, he eventually tried to move up along a small sapling – an evolutionarily helpful instinct for avoiding predators.

Scarlet Tanager Fledgling

Hello, world!

As we were wholly engrossed in our careful stalking of the fledging, we almost forgot to call Tim and Eric to join us. When they finally arrived, armed with a Marantz audio recorder, an extra battery for the camera, and an additional tape for the video camera, our small but extremely excited fan club for the fledging was complete.

Eric Gulson taking an audio recording of begging calls.

Our team spent the next five hours collecting digital media on the fledging, who finally decided to stay on a thin sapling branch (which oscillated up and down every time the male tanager came in to feed his fledgling, leading to some adjustments with the video camera). In the course of those five hours (time does fly when you have a fledgling to occupy your thoughts), Eric found another young Scarlet Tanager fledgling about 6 meters up a maple. This second fledgling was being fed by the female in the territory, indicative of a rather common practice among parent birds of splitting up feeding duties among their fledged young.

Jen Goforth recording a video of the fledgling.

At the end of the field day, we reluctantly left the SCTA5 territory and headed back to the data trailer with our photos, videos, audio recordings, and of course,  some lasting memories – perhaps not of ice cream, but certainly of a very endearing fledgling.

1 Comment

Filed under Birds