Friday, 29 June 2012

Great Crested Grebe Notes/Part Two

17th April Two tiny young chicks on the back of the female as she sat on the nest platform.  They became visible after the male grebe had been with food.  One of the young stretching its neck as the male bird swam away.  The male foraged nearer to the nest than usual and spent time in the reeds.  Perhaps searching there for appropriate invertebrate food for the young.  I’m sure the female will be on the water soon carrying the young.  I wait to see if more youngsters show up!  Only one Swallow seen in area of larger lake.

Hatching is spread over a period of days 25-29 days.  It is 25 days since I saw the birds first incubating

19th April  Wet and cold today and there had been heavy overnight rain.  Nest platform looked very low in water. Both adult grebes on the water today, with female carry what appears to be still two young.  Both young birds seen on the water briefly when male approached to feed them.  On one occasion the male approached with a feather and passed this to one of the young which was seen and photographed at distance with the feather in its bill.

21st April Water levels in lake very high after more rain.  Only one Grebe chick visible today!  Watched as it was fed down feathers by female.  Male grebe continues to seek food in reed-bed and not so much in open water.  Coots that had nested near to grebes now feeding three chicks.  Only one GCG found on larger lake and nesting appears not to have taken place here this year.

The loose and fragile structure of the flank feathers that loosen during preening may play a role in connection with the unique feather eating habit of grebes………Feathers are also fed to their young from the first day.  There is considerable dispute in the literature bout the odd feather eating habit………….The feathers contribute substance to stomach content and enable formation of pellets which are ejected……………Three main advantages of pellet ejection have been suggested. (1) Sharp fish bones are rapidly wrapped up in a felt like substance (preventing damage to the stomach wall) until they are dissolved.  (2) By ejecting pellets, the grebes get rid of indigestible roughage that is left after a meal.  (3) They can minimise the build up of gastric parasite populations, which may represent a considerable health hazard.  The Grebes/J Fjesdsa.

27th April  Water levels high again after more heavy rain during the previous day.  Only one of the Coot chicks seen (numbers had grown to five) and I fear adverse weather may have taken its toll.  The Mute Swan appears to be incubating on the nest hidden in the reeds.  I had been alerted by Sam Hood as to the possibility of there being three GCG young.  In fact there are, and all were on the water today for a short time.  All look fit and well.  The female now moving further from the nest site.

2nd May  All three young on water and calling loudly.  The two smaller birds were soon back on the female’s back.  They eventually joined the male in the area favoured for foraging and all three youngsters were back on the water with both adult birds diving for prey.  Remaining very nervous the birds all made off back towards the area of the reeds on the first sign of any approach by humans.  One youngster seems well in advance of its two siblings.  The Mute Swan continues to incubate.  Numbers of Swallow, Sand Martin and House Martin over the lake today, plus ten Common Terns.

5th May.  One young bird in centre of lake with foraging/diving male.  Two youngsters near reeds with female.  Much calling from all young.  One young spending time on back of female.  Eventually all five birds together in area favoured for foraging.  Adults favouring of young may have already begun.  Greylags appear to be nesting at larger lake.

6th May.  Pair of GCG displaying at Holywell Pond.  Sam suggested they  may be the pair from large lake at Killingworth.  I believe he is probably correct.  CS has long suspected that the second pair of birds at Killingworth were originally the pair from Holywell.  As one of the pair kept disappearing from Killy and one kept appearing intermittingly at Holywell. I belive the birds may have returned to original breeding site following demise of breeding area on floating reed bed.

8th May.  I was alerted by Sam  of large influx of Swifts over Killy Lake and also of all five GCG showing well on smaller lake.  I later found 55+ Sifts (Sam had watched a greater number) which slowly dispersed.  Initially I found only one adult GCG with two young.  There was a significant size difference in the two young.  I think perhaps it was the eldest and youngest of the three.  For over thirty mins there was no sign of the other adult and third young grebe.  There was continuous calling from the other two young, now being fed large fish.  I heard no calling from the third youngster.  This third bird eventually emerged from the reeds with the other adult.  Showing very clearly the fact that the adults have taken over care of different young.  All birds look to be well.

Male and female may each have a favoured chick……..This favouritism is often reinforced as in-chicks try to dominate their siblings……………In the course of the second week the parents may separate, more or less permanently, with one or two chicks each.  The Grebes/J Fjeldsa

20th May.  Watched GCGs for 45 mins and found only 2 young with the adults.  It’s seems one of the youngsters has been lost!  The larger youngster was noisy and continually begging for food whilst the smaller sibling swam quietly and alone by the reeds.  Both adults appeared to be feeding the noisy individual, but by far the main feeding was been done by one adult.

23rd May.  Only two youngsters confirming for definite that their sibling has been lost.  Very clear line seems to be drawn now with each adult feeding a different youngster.

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