Friday 19 September 2014

Ferruginous Duck at Bahri Sewage Pools

Marwa and I were out netting at Bahri Sewage Pools again today. We mainly caught weavers, but there were a few other species mixed in. We had a our first Sedge Warblers of the year and there were more calling from the reed beds. One was already starting to moult its flight feathers after its long journey. There were quite a few Yellow Wagtails around, and we caught two of them. I am still hoping to catch one of the beema Black-headed forms. There were lots of displaying male Northern Red Bishops around, but only a female entered the nets.

Sedge Warbler, Bahri Sewage pools 19th September 2014

Yellow Wagtail, Bahri Sewage pools 19th September 2014

Numbers were still low on the main pools, which we assume to be down to the high turbidity. The water is a thick green colour, which must be difficult for anything that needs to dive for food. We have seen hardly any Little Grebes recently, but there were a few today. The only migrant duck was a Ferruginous Duck, which is our first for the site.

Ferruginous Duck, Bahri Sewage pools 19th September 2014

Friday 12 September 2014

Breeding of African Purple Swamphen finally confirmed

I visited Khartoum Sewage Ponds today with Marwa and we were joined by a couple of friends, Basim and Jeanette. There were lots of terns about, which all appeared to be White-winged, plus quite a few waders, with large numbers of Black-winged Stilt, Ruff, Wood Sandpiper, and Spur-winged Lapwing and smaller numbers of Little Stint, Common Ringed Plover, Kittlitz's Plover, Temminck's Stint, Curlew Sandpiper, Black-tailed Godwit, and Marsh Sandpiper. I had my highest ever count of Hottentot Teal, with 48, plus a few Northern Shovelers.

Northern Shoveler, Khartoum Sewage Pools 12th September 2014

As has so often been the case at this site, the gallinules stole the show. We saw about 8 African Purple Swamphens, which is remarkable for a bird which is generally quite shy. For the last two and a half years we have been hoping to spot a young bird to confirm them as a breeding species, and finally we were in luck today with brief views of a bird in juvenile plumage. There were the usual big numbers of Common Moorhens, and as always there were quite a few young birds present, but for the first time we saw some pairs with very young chicks. I counted 28 Crested Coots, which, as in all previous visits, were in breeding plumage.

Crested Coot, Khartoum Sewage Pools 12th September 2014

Young Moorhen, Hottentot Teals and Crested Coot, Khartoum Sewage Pools 12th September 2014

I am particularly pleased to get the last shot, as, according to the published literature, it could never be Sudan. Common Moorhen is not recorded as a breeder, Hottentot Teal is known from only a single record, and Crested Coot has no published records. I demonstrates how little the avifauna of this country has been studied.

Sunday 7 September 2014

Extensive feather wear of breeding male weavers

We must be nearing the end of the breeding season for the Northern Masked weavers at Bahri, because some of the males have started moulting out of their breeding plumage. I first reported them nesting way back in early February, making it a long season. However, a few birds are still building nests, so it is not yet completely over. Looking at the birds this weekend it was noticeable how worn the wings had become. The very high population density at Bahri means that I don't get many recaptures of ringed birds, but on Friday we caught two - I photograph the wings of every bird I catch, so this gave me a good opportunity to see how their wings have changed.

Male Northern Masked Weaver 158, Bahri 29th March 2014 

Male Northern Masked Weaver 158, Bahri 5th September 2014

The ring of bird 158 in March

The ring of bird 158 in September

Bird 158 (above) was first caught back in March, and then again on Friday. It is clear from the two photos that in the last 6 months the feathers have become highly abraded at the ends, have faded a lot, and that some ends have broken off completely. The effects of bleaching by the sun are equally evident on this bird's leg ring (above). One reason I include the ring shot is to prove that they are the same bird. The above wings are so completely different that I twice went back to my original photos (which include a series of head and body shots), to make sure that there was no mistake. Presumably the greater coverts have been changed recently, as they had narrow white edgings in March and thicker yellow ones in September.

Male Northern Masked Weaver 291, Bahri 23rd May 2014

Male Northern Masked Weaver 291, Bahri 5th September 2014

Bird 291 (above) was already looking quite tattered back in May. In the last few months there has been a lot of additional wear to many of the feathers, but there has also been some attempt at repair, as the broken primary 7 (numbered ascendantly, where the outermost feather is number 1) has clearly been replaced. There was no other sign of primary moult, so this was just a single replacement. However, the tertials and greater coverts are dark centred with bright yellow edgings and therefore must also be new.

Male Northern Masked Weaver 337, Bahri 5th September 2014

Hybrid male Northern Masked x Cinnamon Weaver 329, Bahri 5th September 2014

Many of the other males (above) also showed extensive feather wear and damage. However a comparison with some of the females (below) shows that they seem to have suffered far less.

Female Northern Masked Weaver 326, Bahri 5th September 2014

Female Northern Masked Weaver 334, Bahri 5th September 2014

Female Northern Masked Weaver 338, Bahri 5th September 2014

Although these females have received a lot of abrasion, they lack the more extensive damage seen on most of the males. There must be some behavioural difference causing this such as the activities of males during nest building, or display - where the males hang under nests and flap their wings whenever a female passes. The brushing of the wings on surrounding branches during display must cause some of this damage. There could also be damage caused by aggressive interactions between males, though this is something I have not seen much of, or it could just be that they spend so much time building nests and showing them off to females, that they have little time for feather care.

Juvenile Northern Masked Weaver 333, Bahri 5th September 2014

Juvenile weavers (unlike many other passerine families) have a complete post-juvenile moult, which means that when they moult out of their juvenile plumage they also change their flight feathers (which most passerines do not do). From what we have seen above we know that a lot of wear will occur in the coming breeding season, which helps explain why these birds need to moult their juvenile primaries to ensure that they will last the rest of the year. Juvenile number 333 (above) had already starting to moult its flight feathers (9 is in pin, 10 is three-quarters grown, while 1 to 8 are the old juvenile feathers). However, this bird still has fresh primaries that will easily last it for the next few months, which raises the question of why they need to moult them now. Surely a better strategy would be to moult them at the start of the breeding season, which is when they will already be moulting their body feathers into alternate (breeding) plumage. They would then have a new set of primaries that could more easily cope with the wear and tear of the coming nesting season. I wonder why they do not do this.

Saturday 6 September 2014

Another hybrid weaver at Bahri

For the last two weekends Marwa and I have been netting weavers at Bahri sewage pools. Yesterday we caught our second Cinnamon Weaver x Northern Masked Weaver hybrid. As with the previous one, the underparts had extensive cinnamon colouring and there was a lot of black on the head forming a slight hood - which are Cinnamon Weaver features. However, as with the previous bird, the upperparts were much yellower, and more like Northern Masked. Again, the yellow nape was one of the most conspicuous differences that separated it from Cinnamon (for comparison see the photo of a Cinnamon weaver at the top right in the header of this blog). This hybrid had a wing of 75 mm, which is intermediate between the 76 mm average of male Cinnamon and 74 mm average of male Northern Masked, though there is extensive overlap between the two. See here for the report of the previous hybrid.

Hybrid Cinnamon x Northern Masked Weaver, Bahri 5th September 2014

Hybrid Cinnamon x Northern Masked Weaver, Bahri 5th September 2014

Hybrid Cinnamon x Northern Masked Weaver, Bahri 5th September 2014

The migrants are already starting to move through. Last week we saw a Southern Pochard and a Gargany, there have been reasonable numbers of White-winged Terns and there have been lots of waders of different species. There were quite a few Yellow Wagtails yesterday and we also saw a Wryneck, while last week we saw a Southern Grey Shrike. We have yet to see any warblers though.

Senegal Thick-knee, Bahri 5th September 2014

Village Weaver pecking at a Northern Masked Weaver, Bahri 5th September 2014