Just some notes I've taken earlier this year as I watched the Great Crested Grebes on Killingworth Lake. My thanks to Sam Hood for alerting me to some of the behaviour. I've kept notes back as I didn't wish to encourage more disturbance than necessary. This pair of birds have coped extremely well over recent years considering the situation of the lake and the obvious disturbance that occurs from time to time.
28th February. The pair of Great Crested Grebes was back on the small lake and appearing to examine the area of last years nesting site. I can’t be certain that they had not arrived a day or two earlier. A single Great Crested Grebe appeared also on the larger lake repeating the pattern of 2011 when one bird only appeared here initially.
5th March. I took the opportunity to watch the pair of GCGs on the smaller lake. One of the birds, the female I assumed, was adding to what may have been the base of last years nest. The male was in close proximity seeming to want to ensure all was well. After a while the female climbed onto the nest and after a little hesitation was mounted by the male for all of three seconds. Previously his facial tufts had been spread widely. I couldn’t see the neck and head of the female as they were hidden by reeds, but I expect she had these out-stretched in typical mating fashion. This mating sequence took place twice as I looked on and on each occasion was followed by each bird facing one another closely, shaking heads and bill pointing. The female then continued to add items collected nearby to the nest with the male continuing to look on in close proximity. The pair then swam close to the nest area.
Grebes are only able to copulate on a nest platform (or other firm substrate), but the first inviting is usually done on the water. (The Grebes/J Fjeldsa).
Reversed Mounting. Reversed mounting is confirmed in at least ten species of grebe, so it is probably universal in this group…………Clearly, mounting cannot be used to determine sex in grebes. Ejaculations are not confirmed to occur in reverse mounting, and the function of the behaviour is unknown. (The Grebes/J Fjeldsa)
7th March. Sam H and I found the pair of GCGs on the smaller lake seemed to be having a break between shifts. There was little action as both birds floated around heads under wings. One eventually stretched its head. A little later both birds showed quite well, but swam away from us around the lake, at least one of them making an occasional dive. That was all of the action seen. It wasn’t long before Sam and I realised that the lone GCG on the larger lake has now been joined by another. This is the exact same pattern as last year. Unlike the two birds on the small lake which are well into mating now, this pair was at separate ends of the large lake and seeming to have no contact as yet.
12th March. Mating took place on two occasions on the nest platform and within a short interval.
18th March. Today the pair seemed to be adding material to the nest, after which the female lay on the nest platform, neck out- stretched and mating took place again, followed by the usual face to face head shaking and bill pointing.
23rd March. GCGs now incubating egg/eggs.
Incubation is for 25 to 29 days with young hatching over that period. Therefore first chick can be expected on 16th/17th April if I have witnessed first day of incubation.
26th March. GCGs on larger lake remain apart with no sign of nesting attempt. Pair on smaller lake continue to incubate. Bird on nest stretched prior to moving from nest and allowing mate to take over nest duty at 16:10. I was later told that family had allowed dog into lake and it had been chased off by a Mute Swan which had stick thrown at it by family. GCG off nest had been frightened.
27th March. An egg clearly visible when GCG lifted on nest. Other bird foraging successfully (small fishes caught and eaten) in usual area opposite before spending time near to nest and adding material to nest. Coot continues to nest a few yards away on edge of reeds.
2nd April. For the first time during incubation weather had turned cold and wet. Little to report. Interesting to note that Black Necked Grebes are now back at (undisclosed) breeding site and Sam and I had seen one in breeding plumage earlier in the day. I’m told they had visited a few days earlier and then returned. Or could they simply have been hidden in reeds? I think probably the latter.
4th April I checked on the pair following the extraordinary wintery weather of the previous day which had been continuous sleet, very cold and windy. One bird lay low on the nest. The other bird fished and was followed by two Coots intent on taking any prey caught by the grebe. The grebe called as if to warn coots off. The grebe crouched on water. At 14:10 the grebe swam to nest, the sitting bird stretched and moved on to water to be replaced on nest by partner bird who appeared to do a little tidying of the inside of the nest before sitting. I noted the Coot’s nest which had been on open water appeared to have been flooded and washed away. GCGs nest appears to remain sturdy. Very cold again today, with hail showers. The grebes looked thoroughly soaked. Some sun so hopefully there will be a quick dry out.
Preen oil. Grebes are the only species known where the preen oil contains paraffin, thought probably to aid waterproofing. The Grebes/J Fjeldsa
Additional info. Sam had noted that the female grebe (we assume the smaller bird is the female) is more timid than the male when off the nest foraging. Perhaps to be expected when there are eggs on the nest. Sam has also noted the different style of foraging by the birds on the larger lake (he has seen some display by them) in that dives at centre of lake are much longer than that of the pair on the small lake and that there is more of a tendency to forage near to the edge of the lake early morning and late in day. Perhaps this is simply related to habitat i.e. a larger lake with more undergrowth for hiding prey near to the edges. Where will they nest is the question? Will they nest?
5th April. Cold but sunny, allowing grebes to at least dry out. Noted that I had seen first Swallows in Killingworth 4th April 2011 but none have been noted this year.
6th April. The grebe not on the nest was adding small pieces of weed to it before moving away to forage. Pair of Mute Swans finishing off nest few yards away from nest of grebes. The Coots nest on open water has reappeared. Although water is down a little it looks as though the Coot has been busy rebuilding.
7th April One grebe added small pieces of weed to nest whilst other remained low on nest. The pair of Mute Swans remains in area, but not at nest which appears bulky and finished. Two pairs of Great Spotted Woodpecker in territorial dispute near to nest holes, later examined and entered by female bird. Pair of Bullfinches also in this vicinity.