fish eating birds?

I fish a small stream where i used to catch some nice chub up to 4Ib + when conditions where bad and fishing elsewhere was difficult. This last month i have struggled to even get a bite here when usually fish are very easy to catch. I have noticed some fish eating birds which iam convinced are Gooseanders, the birds are not as large as cormorants and not black but grey/white in colouration. The birds are present when i arrive but quickly take off. There must be 4+ "working" the stream and in places the banks are stained with droppings.

What sort of size fish can these birds take and do you think that these birds could have wiped out the chub stocks?

I wouldn't have thought they'd be able to take a 4lb fish, well not regularly, thats a very big meal. A cormorant can take a fish up to 12 inchs, if the bird you're seeing is smaller than I would guess it will probably eat smaller fish.

I wouldn't be surprised if the birds have stressed the bigger chub out and they've left the stretch. If the birds are still working the stretch then there must be fish for them to eat or they'd leave.

I thought Goosanders had a red brown head ,but i think the grey lag geese are also called goosanders they are black an white

Definitely not greylag geese but are some kind of fish eating bird???

I think you are seeing goosander, also called common merganser. The females have greyish plumage with a rusty red coloured head. The males are creamy white with black and white wings with a streak of yellow and a bottle green head. They are slightly larger than a mallard but slimmer. Their beaks are long and thin with a hook on the end. Their diet is almost entirely fish.....

Red-breasted merganser, 55 cm and goosander, 62 cm are different species: both eat small fish and crustacea, but goosander mainly stays to feed on freshwater in winter. Confusingly, Mergus merganser is the goosander and M serrator is R-B merganser.
Male goosander is markedly black and white, head looks boxy, bill fairly pointed with small down-turned hook on tip. Female and immatures have brown head, males black.
But, you may be seeing winter-plumaged gt crested grebe, c. 40 cm long; longer, more upright neck, no ruff or tufts in winter. Colouration more grey and white than black and white. V little difference between sexes. Again, feed on sml fish and crustacea.
By comparison, cormorant are c. 90 cm long.

Goosanders can get through a lot of small fish in a day but not as many as a cormorant that can scoff over 40 fish per day.

What makes the goosander so efficient is their collective feeding approach. They form a line and sweep up the river driving the fry forward like a net allowing several individuals at a time to dive and feed. I've seen over a dozen at a time feeding like this on the Wye.

Usually a coastal bird that ventured a few miles inland during the winter, they are now a common sight on rivers across the country and are just one more obstacle for the fry to navigate.