Nightingale numbers fall by 91 per cent in 40 years

[rlchew]

I was both surprised and disturbed to hear about the sharp decline in the population of Nightingales in the UK.

Nightingale numbers fall by 91 per cent in 40 years

As I live in Essex, I am fortunate to be able to visit several sites in early May each year and reliably see and hear this superb songster.

I have also seen them at Stodmarsh and Blean Woods in Kent and Minsmere in Suffolk.

I also heard one singing at Lakenheath Fen a few weeks ago whilst looking for the Golden Orioles .... I heard both and saw neither!

Richard

[aeshna5]

In the new issue of British Wildlife it talks of the effect on Nightingale numbers in woods where deer exclosures are used in woods where the songster breeds. Quite dramatic results- with many more Nightingales where the deer are excluded.

I'm sure there are other factors too as I don't think deer can be blamed for a south-easterly retraction of range.

Back in May it was great to hear so many nightingales at Fingrinhoe Wick + was lucky to see a real poser feeding in the open like a Robin at Minsmere.

[RKB]

Originally Posted by aeshna5

I'm sure there are other factors too as I don't think deer can be blamed for a south-easterly retraction of range.

They could, as the SE bias in numbers was already there (due to Nightingale being a 'southern' species). So if the population falls across the board, then it is the SE where they will cling on as that's where more of them were in the first place. For example, if there's 100 in Yorkshire but 1000 in Essex, and the population falls by 91%, that leaves one bird in Yorkshire but 100 in Essex. That's very simplified, but any nation-wide pressure would cause a SE contraction.

It can't be a climate effect, as we're in a very hot few decades with 'southern' species doing very well and new ones colonising (Little Egret etc) while the Nightingale contracts. So the weather is getting better for them - they should be expanding northwards.

[aeshna5]

I think it's being very simplistic to rule out a climatic effect. Yes many southern species like Little Egret have expanded, yet many long distance migrants have declined with climate change often cited as a potential cause.

As you know very well these things are often more complex than a single factor.

[Hobjob]

Originally Posted by aeshna5

I think it's being very simplistic to rule out a climatic effect. Yes many southern species like Little Egret have expanded, yet many long distance migrants have declined with climate change often cited as a potential cause.

As you know very well these things are often more complex than a single factor.

And the climate may be affecting their habitat. Dryness does not give understory and scrub.

Interesting about the Deer exclusions though - have they excluded the ubiquitous muncjac as well? 'cos they clear the understory with very marked browse line.

[RKB]

Originally Posted by Hobjob

And the climate may be affecting their habitat. Dryness does not give understory and scrub.

So why are Nightingales more common around the Med? Two very large national surveys (one of them the RSPB & BTO's Repeat Woodland Bird Survey) showed that understorey actually increased substantially over the past 30 years. As did the amount of woodland. The climate change we have seen over the past half century are not of the kind of magnitude that alters a habitat type to the point where a species cannot use it. It's only of the magnitude where e.g. winter survival of sensitive resident species (e.g. Dartford Warbler) increases due to less frosts. Nightingales are in Africa at this time, so it has no effect on them at all. A hot summer probably suits them when they get back (no waterlogging).

The reasons for citing climate change are also not straightforward. As it's a 'hot topic' then framing a reseach question in terms of climate change means it's more likely to receive funding (and media attention). It is literally a stab in the dark - this isn't a vacuous statement, as I work in this field so I know the ropes. It's not even certain if the Little Egret colonisation is a climate effect or an expansion cf the Collared Dove.

But simple back of an envelope reasoning suggests that the climate is not going against Nightingales. They are on the edge of their range here (possibly as a climate response), but the climate has been getting more 'southern' so they should (if anything) been responding to that positively.

Habitat is likely to be a major factor. In the 1950s and 60s (when population monitoring began) many woods had just been felled and were regenerating as scrub. This scrub is now mature woodland again, which is not Nightingale habitat. This scrub was also the preferred habitat of Tree Pipits, Willow Tits, Willow Warblers and Lesser Redpolls. So all of our population indices start at a piint when the going was particularly good for these species. We have seen a consistent decline since that time, but perhaps if we'd started monitoring in the 1930s we'd have seen a big rise in the 1940-1950s?

Deer may have local effects where there is a high density (such as the one wood where the Nightingale study was conducted), but it cannot be a national effect because understorey has demonstrably increased across the board. And we have no idea what's happening to habitat where Nightingales winter.