Saturday, 10 June 2017

Swans Eggs Infertile

Today I had the sad task of removing Penny and Dukes eggs from the nest. 

Penny has been devotedly incubating them for the past 7 weeks, this was 2 weeks longer than the expected hatching date.
I was concerned for her health as she was losing so much weight and fearful of fatal damage to her organs.
I applied for a Scottish Natural Heritage Wildlife licence to remove the eggs which was granted a couple of days ago. With the huge river spate the other day, it was only today I was able to access the nest site.
Timing was crucial in order to cause no stress to Penny, and she did her bit by getting up and moving to the side of the nest. My 12 year relationship with her proved it's worth, as she was ravenous and ate from my hand as I put the eggs in a bag . Duke stood at the bottom of the island and watched without alarm.
I could not have wished for a smoother operation, with no stress to either of the birds.

                          I got the feeling that Penny was relieved that she could finally vacate the nest and spend time eating and preening, this she did for an hour - the longest period spent off the nest for last 7 weeks. 
After I returned home I opened all the eggs, and as I suspected found no embryos at all, they were just rotten eggs.

Having done some detailed research on swan infertility, it appears there could be 4 reasons for it. One, Duke might be too old, which I discounted because he is younger than Penny and she can still lay 8 eggs. The second reason which is the most credible, is that Duke had a lot of medication during Feb - March when he was ill at the rescue centre. Some of the meds have been known to cause infertility in other species.
The third reason could be that they are related, which is possible and could only be proved by a DNA test of both of them. The fourth reason is interesting, apparently when a Cob loses it's mate and finds another, they are often unable to fertilise eggs with a new mate. This does not hold true for a Pen in the same circumstances ! 
In 10 years this is the first time that Penny has failed to produce cygnets, all due to the death of Popeye last September. We can only hope the infertility is temporary, and all will be well next season. Penny is a remarkable Swan and has laid over 80 eggs in the 10 years on the river, even at 16 years old she is still laying 8 eggs a year. There is no doubt her cygnets will be sorely missed this season, but I for one am happy to have her and Duke gracing our river anyway. I have placed a tennis ball in the centre to give viewers an idea of size, these eggs weigh around 11 ounces each and one is laid every 2 days.

1 comment:

Patsy Goodsir said...

Just traced back your blog to find the reason for no cygnets this year. Thanks for your interesting and detailed explanation. Fingers crossed for better luck next year. Your enthusiasm and love for these wonderful birds shines through.