August 1, 2023
This morning at 08:00 Ken Wiersema, assisted by Dan, Len and myself, arrived at 3 Crabs to conduct the fourth, and final, census on the Purple Martin colony. Bright sun and 5-10 mph winds greeted us as we walked out onto the tide flats. Previous data collections were on July 1, July 7, and July 20.
To see egg and chick counts from each survey in a new window click: 2023 Purple Martin Census. Hint: If possible, drag the new window to the side so you can see the table while you look at each photo. The challenge is to count all the chicks when they are piled on top of each other.
The 18 nest boxes are mounted at the top of the three pilings, about 15' above the sand.
Purple Martin Colony 3 Crabs Beach
To inspect a box, I lean a ladder against the piling, climb up about 10', and insert an endoscope through a small hole in the front of the nest box. I can view what the camera shows on my cell phone, and Ken can view it on his tablet on the ground below. If I place the ladder correctly, I can insert the endoscope into all six nest boxes on the piling. I quickly take pictures, then move to the next piling. So we only disturb the birds for five minutes at each piling.
To see a short (and silent) video of this process in a new window in your web browser click here. The video is 59 MB, so I don't recommend trying to play it on your cell phone. It takes about 15-20 seconds to load.
The "tri-plex" boxes are labeled nA, nB, nC, from top to bottom, so the first piling has 1A, 1B, 1C, 2A, 2B and 2C. The second and third pilings continue the numbering system. We write the box numbers at the back of the nest box to make it easy to identify the box from the photo.
Purple Martins typically lay 4-6 eggs, one per day, generally in the morning. Incubation starts with the second to last egg, so the chicks all hatch within a day or two of each other. Eggs range from 0.8 to 1.1 inches long and 0.6 to 0.8 inches wide. Incubation takes between 15-18 days. This nest had only two eggs on July 1st but six eggs on July 7th, so we wouuld expect these eggs to start hatching in the next 2-5 days. Chicks fledge after 27-36 days.
Today we counted 9 eggs and 57-71 chicks. The higher number assumes that 1-3 chicks are hidden under the pile, based on the number of eggs found in the nest on the previous census. As you can see in the following photo of nest 1A, there are clearly three chicks visible, but there were six eggs and no chicks on the July 20th census. So we have to assume there are either unhatched eggs and/or additional chicks hidden beneath the three visible hatchlings.
Purple Martin Box 1A at 3 Crabs. 8/1/2023
Purple Martin Box 1B at 3 Crabs. 8/1/2023
Nest 1B is empty, but on July 20th there were five fully-developed chicks. So we assume they all fledged successfully.
Purple Martin Box 1C at 3 Crabs. 8/1/2023
On July 20th there were 4 chicks in this box. It looks like there are 5 and possibly 6 now.
Purple Martin Box 2A at 3 Crabs. 8/1/2023
On both July 1st and July 7th, this box had no nest. The grasses we had put in before installing the nest boxes on April 10th had been removed by the Purple Martins, presumably to use in another box. But on July 20th and again today there were six eggs. If they were laid between the 13th and the 20th then they might still hatch.
Purple Martin Box 2B at 3 Crabs. 8/1/2023
Box 2B had 2 eggs on July 1st and 7th, and three on July 20th. It seems unlikely that these eggs will hatch now.
Purple Martin Box 2C at 3 Crabs. 8/1/2023
Purple Martin Box 3A at 3 Crabs. 8/1/2023
Purple Martin Box 3B at 3 Crabs. 8/1/2023
Box 3B had 4 chicks on July 20th, so either a couple are hidden by the two on top or two have fledged.
Purple Martin Box 3C at 3 Crabs. 8/1/2023
Purple Martin Box 4A at 3 Crabs. 8/1/2023
Purple Martin Box 4B at 3 Crabs. 8/1/2023
Purple Martin Box 4C at 3 Crabs. 8/1/2023
Purple Martin Box 5A at 3 Crabs. 8/1/2023
Purple Martin Box 5B at 3 Crabs. 8/1/2023
Purple Martin Box 5C at 3 Crabs. 8/1/2023
Purple Martin Box 6A at 3 Crabs. 8/1/2023
Purple Martin Box 6B at 3 Crabs. 8/1/2023
Purple Martin Box 6C at 3 Crabs. 8/1/2023
If you have Internet Explorer 10 or current versions of Chrome, Firefox, or a new iPad, you should be able to play a short video covering one season (2018) of Purple Martin nesting at 3 Crabs.
Click Here to play the video in your web browser (requires an HTML5-compliant web browser). When you finish, click the HOME button at the bottom left edge of the page, or click the picture of me in the upper left corner of the page, to return to this page.
If the video won't play click here to try it with your system software.