30 Days Wild – Day 9

The moth trap at Blashford was run last night, in fact we run it almost every night and have done so for many years. The advantage of doing survey over long periods is that you get some idea of changes over time. Although one moth trap in one location is not a controlled dataset when the data from lots of traps run all across the country is combined a picture of change begins to emerge.

The longest running systematic survey data for moth comes from the Rothamsted traps, which have been run every night at locations all across the country since 1967. A summary of the results of this work was published (Macgregor, C.J., Williams, J.H., Bell, J.R. et al. Moth biomass increases and decreases over 50 years in Britain. Nat Ecol Evol 3, 1645–1649). The traps are of a standard design so the catches can be compared between sites and between years. It turns out that moth biomass, the total weight of moths of all types caught, actually increased between 1967 and 1982. Since then there has been a steady decline to the present. However there still seems to be almost twice the biomass of moths now that there was in 1967. Catches varied widely between years, with hot, dry years, such as 1976 resulting in large increases, so we might expect increases following the last two summers, time will tell.

Although the data does not go back before 1967 in such a systematic way, the evidence that is available suggests that the really big declines had already happened by 1967, following the large growth in pesticide use in the years following WW2. Comparing habitats the poorest are urban and arable areas, arable perhaps due to their uniformity and continuing pesticide use, urban areas although more diverse are still subject to light and chemical pollution, both of which probably have impacts. More natural habitats such as grassland and woodland have larger catches and might be expected to be more stable, but have actually suffered 18% and 15% decline respectively since 1983. Although numbers are lower, catches have been stable on arable land over the same period.

great oak beauty

great oak beauty – a moth of old woodland

It appears that the continuing declines are ongoing in the richest habitats but stable on the degraded ones, perhaps indicating that all habitats are declining towards an impoverished base level of bio-abundance, at least for moths. A similar pattern is suggested for other insects too and is supported to some degree by observations of long-term changes in bird populations across a range of habitats.

In recent years there has been a lot of enthusiasm for “Rewilding” and this does seem to be one way to start to reverse the wholesale declines impacting many species. It is certainly true that typically small, isolated nature reserves cannot maintain our biodiversity, but they do still have a vital role to play. They are biodiversity islands in a generally impoverished landscape. If the impoverishment can be reversed this biodiversity can start to spread out from the reserves and repopulate the wider countryside and urban areas. Nature reserves are not just slightly nicer bits of countryside, they are where we have effectively “Banked” much of our wildlife and so need special treatment if we are ever to rebuild wildlife richness across the country. Far from being irrelevant in a time of rewilding, nature reserves remain essential to rewidling achieving its full potential.

The breeding season seems to have been a good one for most bird species at Blashford Lakes. There are now well grown broods of little grebe, coot, moorhen and wildfowl all around the reserve.

coot family

coot family

One group that as fared less well are the ground nesters that use the lake shores and islands. Black-headed gulls are nesting only on the few available rafts, for the first time in over a decade none are using the islands. This may be due to predation last season, but in combination with no breeding around the lake shore by lapwing, I suspect that heavy disturbance, especially at night, is a very likely reason. Unfortunately lockdown started just as the breeding season got underway, which might seem a good thing, but it brought a huge increase in nighttime poaching activity on the reserve as people had more time on their hands and legitimate angling sites were closed.

gulls on a raft

Black-headed gulls are doing well on the rafts with lost of fast growing chicks

Luckily poaching activity has now declined again as angling lakes have reopened. Lockdown has seen lots more people out in the countryside and seemingly a much greater value being put on local greenspace, which is all positive. However, as has been widely seen in the media, it also seems to have resulted in a large increase in more careless use. Many reserves have suffered incidents, with fires being perhaps the worst in terms of wildlife impacts. It would perhaps be ironic if, just as more people have recognised the great value of greenspace, inconsiderate use resulted in some of its value being lost. If we value something we should be looking after it, ultimately nature reserve do not look after wildlife, we all do, we have banked some nature on our reserves, not so we can go in and burn a few pounds from time to time, but so we have seed capital to invest in a better future with wildlife across the whole landscape.

I will try and include more pictures and less verbiage in Day 10’s post!

 

Insects on the Up?

The progress of the season has been rather erratic this year, with spells of very warm or even hot weather interspersed with much colder days. Overall I think that we are still a little behind the average of recent years, but it is a very mixed picture.

Sunday was a fine, warm, sunny day with little wind, ideal for insects and I saw my first beautiful demoiselle, broad-bodied chaser, four-spotted chaser and emperor dragonfly of the year. The four-spotted chaser had emerged from the Centre pond, I think th efirst time I have proved that they have done so there, although I have seen individuals there a number of times. Numbers of large red, common blue, azure and blue-tailed damselfly are also continuing to build.

I am trying to look more closely at the bees on the reserve this year, Blashford has a lot of dry ground with sandy slopes, ideal for solitary bees. In fact “brownfield sites” such as Blashford are particularly good for bees as they often have variations in soil type, slopes and banks ideal for nesting.

Andrena bicolor

Andrena bicolor

Gwynne’s mining bee, Andrena bicolor is one of our commonest spring mining bees and also has a summer brood, it is a close relative of the much rarer grey -backed mining bee, Andrena vaga which was found on the reserve for the first time a couple of weeks ago. The rarer species is still around, but not in the same numbers as a fortnight ago, some of them are getting worn now and so look rather like the much commoner ashy mining bee Andrena cineraria.

ashy mining bee excavating

ashy mining bee Andrena cineraria excavating a nest tunnel.

For several years now there has been increasing evidence of an overall decline in total insect abundance, it is very hard to prove absolutely but accounts of declining moth trap catches and a general scarcity of many insects is attested by many. Older people will remember that when travelling any distance by car in the summer it was necessary to clean many squashed insects off the windscreen. Of course more aerodynamic cars may be a factor too. Whatever the reason it has become much harder to find many insect species in the average summer these days. It was pleasing to see a fair few hoverflies out yesterday including a number of Cheilosia species, a rather difficult genus of mainly black species, the identification of the images below maybe open to revision!

Cheilosia bergenstammi male

Cheilosia bergenstammi (male)

Cheilosia impressa

Cheilosia impressa (female)

Despite the warmer days the nights are still quiet cool and so the moth trap has remained quiet. The pick of the catch was a chocolate-tip moth, it is evidently quiet a good year for therm as this was the third we have caught recently.

chocolate-tip

chocolate-tip

The only grasshoppers and crickets about at present are a few tiny nymphs, but this is the time for finding adult groundhoppers, although the only one I saw was a common groundhopper, but at least it posed for a picture.

common groundhopper

common groundhopper

It would be good to think that we are turning a corner in the insect decline, unfortunately I doubt it, I suspect the wider environment is continuing to become less insect friendly. Although some of this is down to the use of very effective insecticides and industrial mono-culture farming, it is also our overall failure to leave any space for them, even where it would be easy to do so.