Tag Archives: nest searching

Nest Searching Tales

The following are several accounts of nest finding by team member Eric Gulson.  We named the nests after the species (RBGR=Rose Breasted Grosbeak, SCTA=Scarlet Tanager) and the order in which the nests were found.

RBGR 4

Earlier in the season, we were working with several Scarlet Tanager nests and one Grosbeak nest. However, one day Cat monitored that Grosbeak nest (RBGR 1) and found that it was abandoned: no adult came during those two hours or ever again.  Because of this, finding a Grosbeak nest became a more pressing matter, and we began looking for more adults. Two days later, Jack and I were heading into the woods on the trail we take every day and I was lingering behind. As I passed a group of shagbark hickories to my right, I heard the Grosbeak call, similar to a sneaker squeaking on a basketball court. Around five meters up a pair was perched, but they immediately left and flew across the corner of a small field, a total of around 20 meters. I followed them and it seemed as though the female was collecting nesting material. She was near the ground, but disappeared momentarily behind a tree. Soon though, to my surprise, they flew back to the group of trees they came from, where the female headed straight up and towards what proved to be a nest under construction. The nest, as if to humiliate us, was over halfway done and directly above the trail. We had passed by it several days straight without taking notice. We immediately began monitoring it and by the end of the field day, it looked considerably less like a platform and had a clear bowl shape. The pair also copulated in a nearby sapling that day, and the flashing of the male’s white rump and wing patches along with its pink underwing coverts was a striking sight.

SCTA 4

One afternoon in late May I decided to stay after everybody had left, because I had my bicycle and did not depend on anybody else for a ride. It was the day after RBGR 1 had abandoned their nest, so I checked on that site before heading headed further south. Here, I heard the chck-brrr of a Scarlet Tanager, followed by two more. Four individuals, two pairs, appeared and I was clearly at their territorial boundary, since one pair stayed around in an oak tree while the other flew south. I lost track of the pair in the oak, but after a while was able to hear the other pair calling and decided to follow them. Here, I found the male in a small tree, while the female was moving around quite near the ground. She was looking around and dropped to the ground, where she hopped around several times and began pulling at something between a leaf and the floor: spider silk. She was collecting the fibers for a nest, but I quickly lost track of her when she left the floor. However, the male was always to be found in a group of small trees and I resolved to visit the next day. I did, and once again found the male in a group of trees and the female on the ground. I lost track of her until I noticed her flying into a group of basswoods, high above the ground. After watching her enter the area and loosing her four times, I finally saw the nest, twelve meters up, on the fork of a major branch. It immediately struck me how obvious its position seemed, with twelve meters of open space between it and the ground, but it still took me two days to find. I was particularly attached to this pair because the male often came quite close to us when we monitored its nest, and both individuals had distinctive patches of yellow on the head, especially the female. Unfortunately, we lost track of them once their chicks fledged.

SCTA 5

We found the nest of Scarlet Tanager 5 quite by accident. Hilary, Justin, and I had just spent hours searching for a new Rose-breasted Grosbeak nest in early June and were returning from a swamp through a different route when Justin heard a Scarlet Tanager to our north. We decided to follow it for a moment because it was near SCTA 4, although further to the east. The male was distinctive, because he had a couple of white spots on his wing, so Hilary decided to try to photograph it, and I began recording a description of its foraging movements in a microphone, trying to keep track of the bird’s every movement. As he approached a beech tree, he suddenly attacked a woodpecker that had been in its branches. Because I had seen grosbeaks and woodpeckers forage side by side, it seemed odd that the tanager would ever chase it off, so I decided that its nest might be nearby. Sure enough, a little to above and to the right of the incident there was a group of twigs and grasses, so I called Justin and kept monitoring the birds foraging behavior. As it turned out, where I was standing was the only one of four places where the nest is visible from the ground, I had been extremely lucky. It also became clear that this one and SCTA 4 were neighbors, because we would hear the males counter-singing in the mornings and were able to walk in a nearly straight line from one nest to the other.

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Spot Mapping

Spot mapping is a relatively simple but efficient method of covering an area of study during a field experiment. Requiring only a GPS and a map of the surrounding area, it allows for marking out of specific locations of interest and determination of more general regions such as territories. As such, learning the proper techniques for effective spot mapping was one of our first objectives as a group. This was true of both the local Tompkins County crew as well as the group signed on for the Borneo trip. In fact, the job fell to us to “train” the Borneo crew during the brief period they stopped in Ithaca between their respective vacations and the start of the expedition. This skill is a valuable one for field biologist everywhere, and after taking a short time to familiarize ourselves with the necessary equipment and techniques it begin our primary means of keeping tabs on our study nests.

Our TOCO crew was supplied with several GPSes for use in spot mapping. These pocket-sized devices were outfitted with a variety of options, but the feature we were most interested in was their ability to take measurements on the Universal Transverse Mercator coordinate system, commonly abbreviated as UTM. Unlike latitude and longitude, UTM measurement takes the distance from set x- and y-coordinates laid out in a grid across the earth. These measurements are referred to as easting and northing, and the GPS has a page that shows these precise measurements. A master map back at our “home base” showed the UTM grids laid out over an aerial view of our study area. This map was then scanned and copied multiple times, then split up into page-sized “zones” for use in the field. To spot map, we would take a GPS and zone maps for the sections of the woodlot we intended to visit, along with a writing implement. At any point of interest, we would simply take the last 3 digits of both measured coordinates and mark them with respect to our gridlines on the map.

This, of course, begs the question of what qualifies as a “point of interest”? The obvious answer is “a nest”, and discovering a nest is definitely grounds for a mark on the map, taking the coordinates from as close to the nest tree as possible for the sake of accuracy. However, as we’ve previously covered, nests can be difficult to find on their own. As such, we used our spot mapping trips to gradually build up an in-depth map of the region, showing us the important “who, what, when, where, and why” of our study subjects. Any observation of a target bird is denoted on the map with its four-letter band code (RBGR for Rose-breasted Grosbeak, SCTA for Scarlet Tanager, etc.). The point for marking it should be measured as accurately as possible, estimating the distance in meters and direction from the observation point to the target. A singing bird is indicated by a circle around the code, while a calling bird is underlined. If the bird is off in a direction where it is difficult to ascertain its exact location, the circle or underline are drawn dashed instead of full. Any additional notes, such as movement, behavior, individual identifiers, and sex are to be noted on the map as well. One behavior that provides us with particularly useful information is the observation of countersinging between rival males. This behavior, where two males in opposing territories sing to each other to defend their turf, indicates a clear territorial boundary. These behaviors and map observations, over time, provide us with a very clear picture of the territories and home ranges of the birds in our research area. Multiple observations on different days help us build a map of the territories these birds defend, providing us with a much more focused starting point for our nest searches.

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