The PMCA Videotapes an Entire Nesting Season Inside a Natural Gourd

Reprinted from:Update 10(3)
James R. Hill, III
Purple Martin Conservation Association

For the second year in a row, the PMCA installed a video surveillance camera INSIDE an active Purple Martin nest cavity outside our headquarters in Edinboro, PA. Our camera was in the upper neck of a natural gourd, aimed straight down. The camera is miniaturized and is only 2-inches long, by 1-inch square. It is state-of-the-art professional equipment designed for rugged field use. It is monochrome, but illuminates the interior (night and day) with 6 infrared diodes, which are invisible to the martins. The idea for doing this came from 1992 PMCA Landlord of the Year, Charles McEwen of Moncton, New Brunswick, who did it with consumer-grade video equipment clear back in 1991. The PMCA has wanted to put a camera in a martin cavity ever since seeing Charles McEwen's setup in 1991. The final motivation to do it came in 1999, when I went to the American Ornithologists' Union annual meeting at Cornell University. I visited the vendor table of Richard Fuhrman of Fuhrman Diversified, Inc., (www.fieldcam.com) and saw his state-of-the-art miniaturized fieldcams. So, in 2000, the PMCA bought a system from Dick Fuhrman and set it up. 2001 is the second season of observation and recording.

We ran the video and audio cables underground, into the office, to a monochrome monitor, and a Sony time-lapse recorder. We documented the entire nesting season, every second of it, night and day, for approximately 75 days, from nest building through fledging. A single 8-hour VHS tape lasts 24 hours because the time-lapse recorder is only recording 20 frames per second instead of 60. The vocalizations they make in the nest and as they enter the nest are quite fascinating. We hoped to learn a great deal that is currently unknown about martin behavior this summer. All of the following images and diary extracts were also updated almost daily on our web site this past season, but are reprinted here in case you missed them.

5-8-01: Drizzle all day and the ASY-F clings to the inside of the entrance hole, looking out. Note the wet puddle in the center of the natural gourd (we've not added any nest material because we want to record them building a nest from scratch). The puddle formed by rain dripping down the hanging wires in through the hanging holes, despite a caulking job attempting to close the holes. This ASY pair has been in this gourd, pair-bonded, since 5/4/01. Camera started on 5/5/01.

5-10-01: Today, the ASY-M and ASY-F brought in about a dozen, flat pieces of nest material, which can be seen in the bottom of the gourd. It is a sunny, warm day. Today is the first day that subadults were seen on Edinboro Lake at neighboring colony sites. In this interior shot, the male is in the nest bowl and the female is perched in the round entrance hole. The male just finished spinning in the nest bowl and pressing his breast against the bottom of the gourd as he did it, instinctively trying to form a bowl.

5-17-01: This ASY pair is still taking their good old time nest building in their natural gourd. They only bring in a few pieces of nest material each day. In this image, they are defending their gourd from another martin that is clinging on the outside of the entrance hole. On the monitor, we hear vocalizations, look over and see both birds shooting into their gourd, turning around and facing the entrance hole, then a 3rd bird appears at the entrance hole. We think it is an unmated SY male.
5/18/01a: Here the female shapes the nest bowl by spreading her wings, scratching with her feet, and pushing her breast against the floor of the natural gourd as she spins against the nest material. The ASY-M (clinging to the outside of the entrance hole) also engages in this behavior when he shapes the nest bowl.

5/18/01b: Here the nestbuilding adult female "weaves" in a piece of straw. She repeatedly and rapidly vibrates her beak as she places the plant material. Both sexes do this behavior, also.

5/24/01: Today our ASY-F lays her first egg (that's it just below her tail and wing tips). Later, the male brings in lots of willow and cherry leaves to "bury" and cover the egg. Covering the eggs until the clutch is nearly complete (and incubation begins) is an adaptation to hide the eggs from egg predators, since the egg will remain totally unattended most of the day while the female is out foraging to replenish her reserves so she can lay the next egg tomorrow morning.

5/29/01: This morning the female (on left) lays her 6th egg. Incubation has begun (intermittently) with the 6th egg (she did not incubate her 5 eggs at all yesterday, despite cool temperatures. In fact, the eggs were totally covered with leaves and other nest material.) The male sits beside her looking out the hole.

6/08/01: The female is well into her incubation. She spends most of her day just sitting on her eggs. She only takes a few brief breaks each hour to go gather food for herself and to bring in fresh green leaves. Her mate also makes several trips a day to bring in green leaves. She works many of the leaves in her beak, seemingly making them more pliable, or to release more water vapor for nest chamber humidity control, or to release more hydrocyanic acid to reduce the number of nest parasites. Here she is sitting tight on her eggs. She rolls them many times an hour to increase their hatchability.

6/12/01: According to the Prognosticator calculator wheel, a 6-egg clutch initiated on 5/24/01 should begin hatching on 6/13/01. However, the weather was very cold during that initial week of incubation and the female did not spend much time on the eggs. During such conditions, eggs can take 17-24 days to hatch, instead of the normal 16. We'll just have to see what happens. In this photo, you can see the hundreds of fresh green leaves the male and female martins have been bringing in daily and tucking under their eggs.
6/15/01: Today, 17 days after the last egg was laid, our web cam babies began to hatch. One was already hatched when we checked in at 0659 hrs. The second egg hatched while we were watching the monitor at 0847 hrs. The third egg hatched at 1105 hrs. As of 1500 hrs., no additional hatching has occurred. In this photo, the female picks up an eggshell hemisphere from a newly hatched egg and is eating it. The male, looking in from the entrance hole, is watching. We observe both the male and the female eat 3 such hemispheres after crushing them in their beaks a few times. The male flies off with one additional hemisphere in his beak, presumably to drop it away from the colony site. A couple of these hatch eggshells had worked their way onto the unhatched eggs, a potentially lethal condition known as "egg capping," which can prevent the capped egg from hatching. Fortunately, the caps fall off and the adults eat them. The parents begin feeding the young immediately upon hatching. Both parents hold the tiny prey in their beaks and chirp at the youngsters to get them to gape. The male is already feeding the HD (hatching day) youngsters full-sized damselflies.

6/18/01a: The six nestlings are 3 days old today. Both parents are brooding them, feeding them, and eating their fecal sacs. In this photo, an adult female blowfly is exploring the nest bowl to lay some eggs (see dark fly just left of center). In a few days, blood-feeding, parasitic maggots will hatch and begin feeding on the nestlings. Some martin nests will contain hundreds of these fly maggots, which grow to be at least 3/8 of an inch long before turning into a pupae near the time the baby martins are due to fledge.

6/18/01b: The six nestlings are 3 days old today. Notice the way they cuddle for warmth. At this age, they are incapable of keeping warm without being brooded by a parent. Here the adult female is on her way in to sit on the young to brood them.

6/18/01c: In this image, the adult male is brooding his six 3-day-old young. Notice the way he is "mantling" the young by spreading his wings.

6/19/01a: Today the six nestlings are 4 days old. Ambient outside temperature is 88 degrees F. here in Edinboro, PA. These nestlings are engaging in a common behavior that they do in hot temperatures: they are spacing themselves out (instead of cuddling) in the nest bowl with their heads pointed out, their butts in. They are maximizing their spacing and minimizing their skin contact with each other to help thermoregulate (control their body temperatures). Their ASY-F mother looks on.

6/19/01b: This afternoon, to our surprise, the bachelor subadult male that has shown a great fascination with the contents of this gourd (he's been inside several times and has been rebuffed aggressively many times by the adult female) enters the unprotected nest while both parents are out foraging. He proceeds to violently grab one nestling by its throat and bite it, then poke at its still-shut eyes. He moves over and pokes, stabs, and bites two other nestlings. He stays in the nest 5-6 minutes until the adult male returns with food. Amazingly, the nestlings are unharmed and feed normally in the following hours. About 30 minutes after that first encounter, the subadult male returns, but leaves before resuming (?) his violence because a parent returns with food for the nestlings. We will watch closely to see if this SY-M has true infanticidal intents. In Tree Swallows, Barn Swallows, and Cliff Swallows, bachelor males are known to kill entire broods of young to break up the pair-bond in hopes of acquiring a mate. In this photo, the SY-M looks up at the camera.

6/21/01: The young are 6 days old today. Here the female is brooding the young in the cool morning air. Since her 6 young have grown too large for her to now cover simultaneously, here she "mantles" them, spreading her wing open to assist in covering them.

6/25/01: The six young are now 10 days old. Here the adult female feeds one of the gaping mouths. After feeding, she will search underneath the young for newly-voided fecal sacs to remove.

6/26/01: Today the 6 young are 11 days old. Here the adult male sits in the entrance hole after just feeding his young. After every feeding, the parents dig around underneath each young, searching for fecal sacs to remove. They also pick up dropped insect prey (which run all around the nest) and feed them to their young. When the parents bring in beakfuls of small, live moths (which still beat their wings rapidly), the wing scales of these insects float all over the inside of the gourd making a "falling snowflake-like" appearance inside the cavity. Once the martin dropped a Red Admiral butterfly and it started flying all around the inside of the gourd. The bird chased it down and poked the butterfly down the throat of one of its young.
6/28/01a: Today the six young are 13 days old. Here they are shown with their heads out the entrance hole, waiting to be fed. Yesterday, when they were just 12 days old, was the first we noticed them approaching the entrance hole to be fed. Also, as 12 day olds, we noticed them for the first time turning around to void a fecal sac just below the entrance hole, inside the nest cavity. The parents, who sometimes now don't enter the nest to feed the young, just feed them at the entrance hole from the outside and reach in to remove these conveniently placed fecal sacs.

6/28/01b: This shot, taken at 9:53 PM, after both parents have come in for the night and have gone to sleep, shows the male bird at top, sleeping in a vertical position (mostly off camera), up the side wall of the gourd. He's clinging just like a Chimney Swift. He has slept in this same sidewall, vertical-clinging position every night since the female laid her eggs. Before that, she slept in this spot and position. The female is shown just above the cuddled nestlings. She no longer is brooding them, as they are 13 days old and it is a warm night (74 degrees F.). Interestingly, they are still making their food-begging calls, loud enough for an owl to hear them. They finally quieted down about 10:00 PM. Perhaps this is why it seems Great Horned Owls often hit between 9:30 and 10:00 PM; they can hear which nests are active. Starting about this time, I notice several mosquitoes enter the pitch-black nests (it's only pitch black to the birds, not the camera, which uses infrared illumination). The mosquitoes tormented the birds, biting them. Tonight, after 20+ years of martin research, I saw my first martin eat(?) a mosquito. In the dark, the female bill-snapped at the buzzing mosquito, using sound-location only, and got the pest on the third try. I assume she swallowed it and that her intent was not to acquire a late night snack, but instead to prevent it from biting her.

7/4/01: This photo is taken at 9:50 PM, July 4th, 2001, just as Edinboro's 34-minute fireworks display begins. The fireworks are set off about 1/4 mile from the martins, out on a peninsula sticking into Edinboro Lake. The martins in the webcam gourd are in a gourd rack, adjacent to the peninsula, right near the shoreline. The martins couldn't be much closer to the action. The rapid-fire bursts of light, and the massive decibels of percussive blasts fail to rouse them. Here the male is sleeping at top, clinging vertically to the sidewall of gourd like a swift, the female is at far left, and the six young are in the center. The dark entrance hole is to right. When the first of about 200+ blasts went off, the sleeping birds only made a minor twitch. None of the other blasts even wake them. I can see blasts of light entering the gourd and can feel the earth shake. As I've believed all along, fireworks at night are just like a lightning and thunderstorm to martins and it doesn't seem to faze them. Of course, this doesn't mean that you should allow strings of firecrackers to be set off right under your martin housing. No telling what effect that would have!

7/9/01: Today the young are 24 days old. They are spending a great deal of time preening their new feathers and stretching their wings. At one point today, the colony went into a panic and flew around giving alarms calls because a human walked under the gourd rack. When the parents gave the alarm call, the six young scrambled to the back edge of the gourd, diving under each other for safety. This is an instinctual response; trying to get as far away as possible from the entrance hole and the reach of predators.

7/10/01: The young are now 25 days old. Here, two are awake at 8:24 AM, sitting with their heads out the entrance hole waiting to be fed; their four sibs are asleep, cuddled up against each other.

7/12/01a: Today the young are 27 days old. They spend a lot of time flapping their wings, exercising them in preparation for their maiden flight. These "flapathons," as we call them, kick up a lot of nest debris (dried fecal material, disintegrated feather sheaths, insect wing scales, etc.), which the nestlings no doubt breathe. Reason enough not to use Sevin or DE insecticidal powders in martin nests.

7/12/01b: Here all six of the 27-day-old nestlings scramble to the entrance hole, flutter their wings aggressively, and vocally beg for food from the hole-clinging parent.

7/15/01a: The six young are 30 days old today and haven't fledged yet. Here one nestling sits on the back of its sib at the entrance hole.

7/15/01b: This shot was taken at 11:47PM, and shows 9 birds sleeping in the gourd, one being a "lost" new fledgling.

Fledging and Post-fledging: Two young fledge at 32 days of age (7/17); two more at 34 days of age (7/19); and the last two at 35 days of age (7/21). Some fledglings continued to sleep in the gourd at night through the morning of 7/29/01. Parents engage in post-breeding nest-cavity defense during part of this period.


Copyright 1998 by Purple Martin Conservation Association. All Rights Reserved.

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