Candling

Today I checked the eggs in the East and West nests and removed eggs that were not developed. As I’ve mentioned, I have marked the eggs that were added late and except for one original egg (perhaps infertile) all of those removed were added later, after incubation started. There still will probably be some unhatched eggs since some that I did leave were marked as being late, but if there was any possibility that they would hatch – if a duckling had developed – then I left them in the nest.

The count now:
East nest: 17 eggs (removed one) hatching next week, between Sunday and Thursday
West nest: 13 eggs (removed 4) hatching between Thursday 6 days from now and Monday
South nest: 10 hooded merganser and 1 wood duck hatching in the first week of June

Checking eggs for development is called “candling” because in olden days a candle flame was used as a light source. I use a very bright LED flashlight.

There is a bracket beneath those two holes that holds the flashlight. It shines upwards and illuminates both holes equally.

It’s easy to see a difference. A growing duckling inside the top egg blocks the light. The bottom one is undeveloped.

Mergansers around June 3rd

The hooded merganser in the South nest started incubating on May 4th so hatching should occur 30 days later, plus or minus a few days. She still has only the eggs she started with: 10 hooded merganser eggs and 1 wood duck egg. No eggs have been dumped in her nest, so all 11 should be on-schedule to hatch together.

In the East nest several eggs were added by other wood ducks more than a week after incubation started. I can identify them: When incubation starts then, the first time the duck is away for food, I use a marker to put a tiny dot on the end of the each egg. As eggs are added (dumped) by other ducks and again, when I catch a time when the duck is away, I mark the additions with two dots, then three dots, etc. A few days ago I removed 4 eggs that have zero chance of hatching on time, so she now has 18 instead of 22.

In the West nest there are still 17 wood duck eggs: 12 that she started with, 2 more that were added not long after incubation began, and 3 that were added later.

If you go to the Live Cameras page, there is a “Status” button that will show a summary that I update somewhat more often than blog postings. It now shows the estimated hatch date for each nest. They are:

  • East: May 17th (sometime between the 14th to 20th)
  • West: May 21st (18th to 24th)
  • South: June 3rd (1st to 6th)

West nest today: the 12 original eggs (left), 2 added somewhat later (bottom) and 3 added later yet. They all went back into the nest.

Merganser starts soon

All of the ducks were away this afternoon so I checked the nests. Other wood ducks continue to add eggs to the East and West nests. East now has 22, two more since Friday. West now has 17, three more since Friday. These new eggs have no chance of hatching on time. I will remove those that are a lost cause sometime in the near future. My previous post on Friday described what is going on with the added eggs.

The hooded merganser using the South nest now has 8 eggs and has started to add down which means incubation will begin soon. Right now the eggs are outdoors-cool and thus dormant. A wood duck also has layed an egg in the South nest in time for it to be incubated, so I expect there will be at leasts one woodie in with the hoodie ducklings. Again see my previous post and also this site’s Ducks Info page for more about the odd blended-family habits of wood ducks and hooded mergansers.

South nest: 8 are hooded merganser eggs, the top center egg is a wood duck’s.

A wood duck egg (left) is smaller and tan; a hooded merganser egg is larger, more rounded, and white.

20-14-7

All three nest boxes were occupied at about 2:00pm on Friday. Here’s a link to the camera page.

As of Friday there were more eggs in each nest box vs. when I last checked on Monday:

  • 20 eggs in the East nest – 5 more than on Monday
  • 14 wood duck eggs in the West nest – 2 more
  • 7 hooded merganser eggs in the South nest – 3 more

The hooded merganser is laying one egg every 2 days. They are larger, whiter, and more round than wood duck eggs.

The hooded merganser is usually in the nest box for about 90 minutes each time. She’ll start incubation in the next week or so. Wood ducks have visited the South nest briefly but have not left any eggs so far.

The new eggs in the East and West nests have been provided by other wood ducks because the incubating duck was all done laying when incubation started. Both wood ducks and hooded mergansers lay eggs in multiple nests. The biologist’s term for this is “dumping”. Here is more information about it. Dumping is partly a way for a duck to improve the chance that her offspring might survive even if something happens to her: fox, coyote, eagle, bird flu, etc. It also can be due to a shortage of nesting sites. However it works only for eggs deposited before incubation begins because eggs added more recently will not develop in time to hatch with the others – the duck family leaves the nest the day after hatching and they never return.

Sometimes dumping that happens after the start of incubation will occur when the incubating duck is out getting food but frequently there will be 2 ducks in the nest box together. Once in a while this is peaceful (see this video) but often there is a scuffle (as in this video) where the resident tries to repel the invader. If the invading duck leaves an egg the incubating duck will always follow her instinct to add it into the clutch and incubate it with the others. One duck does all of the incubating and then for about 2 months she takes care of all the ducklings that hatch: her own, those of other ducks, and sometimes a mix of wood duck and hooded merganser ducklings.

Incubation Two Too

I’ve been watching and checking the duck in the West nest. She’s been on the nest overnight but away for many hours each day. When I checked the eggs two days ago they were cool even though she had been in there a lot. But yesterday morning the eggs finally were warm and she was gone for only a few hours today. Therefore my guess is the incubation start date for the West nest is yesterday which would make the ducklings due on about May 21st, plus or minus a few days. She had 11 eggs yesterday morning.

In the East nest it’s incubation-as-usual. She had 15 eggs the last time I checked. Ducklings are due on about May 17th. She was half buried in her down blanket for a while today; it looked snuggly.

The South nest had just a single hooded merganser egg over several days early this week. The merganser was there for an hour on Wednesday and not there at all on Thursday. But when I looked at today’s recording while writing this it showed that this morning she was there for about 90 minutes so I’m on my way out (9:20pm) to check …

… and Yes! There are three hooded merganser eggs now. You can see them just above the large paw of the strange creature who has invaded the nest box and is feeling around in the wood shavings to see if there are any more. (The ducks don’t mind and actually can’t tell that I’ve done that … … as long as they aren’t home when I open the box! I always check the camera first, of course.)

We really hope the merganser continues and will use this nest again as she did last year and the year before too. (It’s probably the same duck because they’re likely to re-use nest sites where they were previously successful.) It’s fun to have some hoodies along with the woodies. There are pictures of both species at the very top of the birdsgv.com main page in a small gallery of 6 images that scrolls sideways. The first picture is a wood duck pair, male and female; the fifth picture is a male and female hooded merganser pair.

This is a screen shot of the web site’s live view of the two nests earlier today. You can watch the excitement of ducks sitting and sleeping too: go to birdsgv.com, scroll down, and click/touch the “View Live Cameras” button.