A cold, wet, passage to Spring this year!

You can now sit, with a coffee in the Market Square and watch Peregrine Falcons, the world’s fastest flying bird! I often mention Peregrines but their breeding success in lowland England is a
remarkable success story. In the late 1960’s the only “twitchable” Peregrines were a pair in a quarry behind Aviemore in Highland Scotland and a national population of about 60 pairs! The latest survey has located 1769 breeding pairs in the UK, the majority in lowland counties and a 22% increase on the 2002 census. They are still vulnerable to persecution – as the gun shot injury to one of the Cambridge bred birds in 2017 shows – and there has been a decrease in upland areas associated with moorland management.

Where’s the Peregrine …….? …….on the Kings College spire to the right of Great St Mary’s tower

I think my guestimate of 15-20 breeding pairs of Sparrowhawks in our study area is too high. Five to ten pairs are more realistic. Sparrowhawks became extinct in Cambridgeshire in 1960 due to agricultural pesticide poisoning but returned in 1985. If/when it warms birds will be displaying over Cherry Hinton, Milton Road, Arbury and the City centre.

I think there are at least two pairs of breeding Buzzards in our area. Buzzards returned to breed in Cambridgeshire in 1999 and are now, probably, our commonest raptor. Sit on Madingley Hill just outside our study area on a warm day in April for an hour overlooking Girton and Eddington and from Histon to Over and you can count over 20 individuals soaring in the thermals plus 2-3 Sparrowhawks and Kestrels (and maybe even a Raven or two!).

The Red-legged Partridge in a garden in Cavendish Avenue was probably looking for food during the recent freezing weather.

The Black-headed Gulls along the river have halved in number and mostly developed their brown hoods and are filtering back to their breeding sites. The mud churned by the runners and their families on Midsummer Common after the Half Marathon on March 4th provided a late bounty of available earthworm food; the grass soon grew back and by third week of March had 90% recovered.

Jesus Lock – March 2018 Black-headed Gulls with brown hoods!

Local Rookery with active nesting

A Kingfisher over Magdalene Bridge during morning rush hour on 31st March was heading upstream, probably to a nest site. Blackcaps are still being reported from East Chesterton, Glisson Road Area, Cavendish Avenue (probably two males) and two males and a female off Huntingdon Road – one male that delivered a muted sub-song has now burst into full song; a male was singing in
Logan’s Meadow on 12 April. Chiffchaffs were singing in Huntingdon Road, Logan’s Meadow and the Cambridge Business Park in Chesterton on 12 April. Sadly, the singing Chesterton Siskin has gone. Goldcrests are now singing from the smallest and isolated conifer trees from Coldham’s Lane to St Albans Way to De Freville to Histon Road and Roseford Road; many trees have their own self-sustaining population and the larger groups also have Coal Tits. I can no longer hear bats but I can still hear the high trill of Goldcrests, some birders cannot! If the song does not end in a flourish check out for Firecrest!

I have now 18 Mistle Thrush sites across our study area (thanks Sam Buckton, Michael Holdsworth and Martin Walters); please keep sending me your records. I didn’t realise Mistle Thrush has become a red listed species – a species that has declined by 50% in the last 25 years with no sign of recovery. Rhona Watson has sent me brilliant shots from Jesus College. Sadly, a Fieldfare forced into town to look for garden berries during the recent frosts was knobbled by a cat! Wintering thrushes are usually very timid but I have seen them in their breeding grounds in Scandinavia and Poland where they are very confiding and can be closely approached.

I have finally located the Newnham Heronry. I could only see three active nests but this is Olwen’s “manor”.

This year 111 apparently active Rooks nests (108 in 2017) have been counted. They are interesting to watch. One bird sits by the nest while the second bird looks for sticks and twigs for the nest. If the nest is left unguarded neighbours pillage it for their own nests! I cannot understand why there are no rookeries in Trumpington/ Byron’s Pool area. I think the loss of elms and sustained persecution since the 1960’s could be the reasons (see below).

The edge of the Dickerson Pit at Milton Country Park just comes into our project area. The female Scaup (found by Jon Heath) was still there on 22nd March.

Now is the time to locate House Sparrow nest sites. I carried out a City survey in January to March 2013 and January to April 2014, of the breeding population of House Sparrows in the political wards of Cambridge City. I found 733 “active nests” and an estimated total population of 1000 pairs based on numbers of birds counted.

I concluded that distribution is determined by nest site availability and the need to maintain an interconnecting colony. The minimum colony size is three “active nests”. Removal of ivy from walls, home improvements which prevent access to loft space and housing built since the mid 1990’s with sealed, insulated lofts prevent access and nesting. Colony survival is as important as nest site availability. If nest sites are lost, colonies break down and fail and the population declines. There is a mutual relationship between House Sparrows and Starlings. Sparrowhawk predation is not a cause of House Sparrow decline. Cherry Hinton had the largest House Sparrow breeding population, Trumpington the smallest. I need to do another survey ….. sometime!

If you have House Sparrows and need to insulate your roof do put up nest boxes – a three box terrace is best and at gutter height facing east. South facing sites are often ignored because they risk overheating in the summer! The best place to buy a bird nest box is: John Stimpson, 53 Twentypence Rd, Wilburton, Ely CB63PU – 01353740451: from Cottenham up the hill into Wilburton, on the right usually with an “A-frame” notice outside.

The lack of House Sparrows and Rooks, two species of open farmland, in Trumpington/Granchester is worrying. In the 1960’s – early 1980’s there were so many House Sparrows feeding on the cereals yield trials from August to September at the Plant Breeding Institute (PBI) – now Trumpington Meadows – a farmworker was a dedicated sparrow killer! The PBI is no more, as are the House Sparrows. It was probably the move to winter cereals and winter Oilseed Rape from the late 1970’s onwards doing away with over-winter stubbles that was responsible for the demise of the House Sparrow; did the same happened to Rooks?

Listen for Black Redstarts and their strange song that sounds like ball bearings being “scrunched” together. Why they are not common here is a mystery. Travel to France and you will see them at the first service station you stop at! Spring/summer visitors are arriving! Sand Martins are about; keep watch for passage Wheatears and Ring Ousels on open fields particularly Trumpington Meadows and Hobson’s Park. Tawny Owls are hooting. Reed and Sedge Warblers are in but so far in small numbers. First Brimstone butterfly on 27th February gave false hope for a warm spring!

Bob Jarman

12 April 2018