MWT
Ospreys typically lay a clutch of two or three eggs, they can lay up to four but we have never seen that here on the Dyfi. The eggs are a little bit bigger than a large chicken egg and are cream in colour with brownish-red speckles (maculation).
Over the years of collecting our egg-data we have observed all sorts of unusual occurrences including eggs that didn't hatch, chicks from egg-number-two hatching before their sibling in egg-number-one and eggs that have been almost pure white.
Unhatched eggs have been removed from the nest, under licence, during the ringing process and have been sent off for scientific analysis. The unhatched egg from the 2020 clutch is on display in the Dyfi Wildlife Centre on the Family Tree wall.
The table below shows the details of every egg laid at the Dyfi nest.
First mating to first egg
Below is a chart illustrating the time elapsed from first mating to first egg each year, associated with the respective osprey pairing from 2011 onwards.
Telyn and Idris have shorter periods than when Monty was with us, suggesting (albeit anecdotally from a small sub-sample) the male also influences this first egg timescale.
1st Mating to 1st Egg each year
The chart below shows how long a Dyfi female osprey takes to produce each egg, from egg two onwards (egg 1 is not shown as obviously we don't know when each female flicked on the egg-making switch).
- 73.3 Hours - Egg 2 Average
- 69.5 Hours - Egg 3 Average
So an almost 4-hour shortening in time to produce the third egg vs Egg 2. I guess it would be safe to assume from this, the actual Egg 1 time would be north of 73 hours - possibly 75 or even 76 hours?
*Note: the longer time than usual in 2014 was almost certainly down to interference from another competing female - Blue 24
Egg 2 and 3 production times
Ospreys incubate their eggs for around 37 days. The female does most of the incubating and the male brings her fish while she is on the nest. The male will incubate while the female is eating or bathing away from the nest. It there is an intruding osprey or other threat to the nest then both birds will defend the eggs if they're around.
The chart below shows the incubation times for all our osprey eggs.
Delayed Incubation vs Standard Incubation
This chart below illustrates two very different reproductive strategies with regard to incubation.
Nora (2011/12) and Telyn (2018/19) did not incubate the first and second eggs fully until they had laid a third. This ensures that if all three chicks hatch, they do so very near to each other in time.
Glesni (2013 - 2017) on the other hand incubated immediately after laying her first egg - this results in a more spread out hatching sequence.
The comparison table below is for all three-egg clutch years only, so that we're comparing apples with apples. The average hatch spread for Nora was just 2.1 days and Telyn 2.6 days, whereas the hatch-spread for Glesni's three chicks was approximately double, 4.5 days.
Hatching spans of Dyfi three-chick broods