How does wildlife (& surveyors) cope with an un-sprung Spring?

How do both wildlife and surveyors cope when the spring throws a curve-ball? Late-April in Wester Ross.

How do both wildlife and surveyors cope when the spring throws a curve-ball? Late-April in Wester Ross.

As an ecologist, spring is an exciting time of year. Things are happening, changes are occurring everywhere and rapidly, and the doldrums of winter are finally coming to an end. It is also an incredibly varied season weather-wise and prone to throwing many, and often large, spanners in the works when it comes to fieldwork.

Statutory bodies and expert organisations provide as much guidance as they can when it comes to undertaking fieldwork in the correct season, however, that season can be incredibly different depending on where in Britain you’re based. This spring has been a classic example of that. With work everywhere from northern Scotland, to Wales and East Anglia, BiOME have seen just what a difference a few hundred miles can make. Survey work in Wales saw us enjoying many regular summer migrant birds; Wood Warblers and Redstarts, whilst most spring butterflies were on the wing ‘on time’ including a large emergence of Green Hairstreaks, yet despite having left our fieldwork in Scotland until the end of each month we have been subjected to the fickle nature of our weather, including no less than five inches of snow and torrential rain! The response of birds to this is fascinating with species such as Wheatear and Ring Ouzel dropping in to valley bases and even moving to the coast. However, this year the populations of these species appear to have been badly hit with still no recovery apparent in May after this early exodus.  A good marker of the advancement of spring in Scotland is the distribution of Ptarmigan on the hills. These high-altitude specialists were still as low as 600m within our survey area on 20th May, normally a mid-winter altitude.

Whilst Green Hairstreaks emerged en-masse and Early Purple Orchids (below) bloomed, species up in northern Scotland are still struggling to start the breeding/flowering/flying season

Whilst Green Hairstreaks emerged en-masse and Early Purple Orchids (below) bloomed, species up in northern Scotland are still struggling to start the breeding/flowering/flying season

Early Purple Orchid

So, how on earth do you go about planning survey work when the weather can be so variable? It’s incredible difficult, but in general we feel that spring is about six weeks behind southern England in northern Scotland, and even as much as two months behind in some areas. In fact the entire season ‘down south’ is a protracted one with many species starting to breed early, whilst others don’t start until much later, however in northern Scotland spring is a rush! It generally starts with a bang in mid-April-early May when everything seems to arrive and breed at once. When it comes to birds, many can have attempted to breed, failed and left again by mid-June! Most insects and flowers delay their emergence until June, July and August with alpine specialists often not in full bloom until August, just as the landscapes of the south are turning a sun-roasted brown. All this can make planning fieldwork difficult especially as some species may only be present on their breeding grounds for a few weeks, but after many years of experience we feel with have a good handle on exactly when to be where.

A female Ptarmigan down at 600m in late May, considerably lower than it should be!

A female Ptarmigan down at 600m in late May, considerably lower than it should be!

A late-April day in Scotland! We are hoping that days like this will now be saved until next winter.

A late-April day in Scotland! We are hoping that days like this will now be saved until next winter.

What the rest of the summer holds is yet to be seen but we can only hope that many species which are currently absent from the high tops in northern Scotland will return, and that the weather doesn’t throw any more curve-balls!