The most important cue to observe when nest-searching is bird behavior. Cape Sable seaside sparrows nest in grass cups in the marl prairies of the Everglades, so finding their nest without watching them can be nearly impossible. Nest-finding has been my favorite aspect of all of my positions as a field technician, so I want to share what I believe is one of the most rewarding days in the field: finding a nest.
When we know where there is a breeding pair, we go to the territory area first thing in the morning and watch the pair. It is not unusual to spend a whole day’s work trying to find one nest, especially if the female is on eggs. It’s the easiest to find a nest when there are nestlings because the adults are making constant trips to the nest with food as long as no one is too close to the nest. If they aren’t going to a nest and are constantly chipping, we back away. They generally will calm down and go feed their young once we are about 30 meters from the nest area. Once we see the adults go into the grasses a few times, we can get a good idea of where the nest is. Flagging areas around where they disappeared into the grasses can help as a reference point.
Finding a nest with eggs tends to be more difficult. The female only gets off the nest every 40 minutes to eat, so you have to be watching the right area to know when she is off. She will come back after ten to twenty minutes, which is when it is very important to watch where she goes. Once we see her disappear, we walk to the area to see if we can flush her off the nest and have an easy find. Often that doesn’t happen, so we flag the area and wait for her next feeding trip where we can observe how close she is to our reference point and at what angle. This makes it much easier to find the nest the second (or third…or fourth) go around. Once we are pretty confident about the area where the nest is, we search the grass clumps for a grass cup containing eggs or nestlings.
Once we find the nest, we want to spend as little as time there as to not cause too much disturbance. We take a GPS point and put two flags low in the grass on opposite sides of the nest about three meters away from the actual nest cup, and one flag on high grass a minimum of five meters from the nest. This aids us in finding the nest when returning to check the status the following week. We add an iButton, which takes temperature readings every fifteen minutes. Adding the iButton allows us to make less frequent visits to the nest by providing us the date of the outcome without having to check the contents as often. After those steps we walk further away and fill out a nest card with details about the nest that we update with each visit.
Those are the basics of what we do to find a nest. It takes a lot of patience and good observation skills. Monitoring the nests gives us information about the survival rates and the population trend based on their reproductive success.
The season is about halfway through, and we have found 22 nests. Out of these, 10 have been successful, seven failed, and five are still active.