As we welcome the official start of spring and all its wildlife glory, we'll be looking through the eyes of the corn bunting over the next couple of days, courtesy of some dedicated effort by farmers and RSPB staff in the South West of England. Today, we focus on spring and summer, but look out for autumn and winter tomorrow!
Image: Lower Pertwood by David White
Tucked away near Salisbury Plain in south-west Wiltshire, the 2,100 acres of Lower Pertwood was a sheep farm until WWII. However in line with the vast majority of livestock farms at this time, a lot of permanent grassland was ploughed up to grow crops for the war effort. About 25 years ago the farm became organic and currently the split is about 50:50 between arable and grassland, most of which is chalk downland. The arable rotation is largely based around spring and winter oats with leys of rye grass and red clover. All of which benefit corn buntings at various stages of the year.
Spring
In April things are greening up at Lower Pertwood, the last of the crops are going in the ground, having checked the fields for nesting lapwing and stone-curlew. The winter crops and leys start to provide cover for nesting skylarks and the corn buntings are singing more and more, despite there still being large winter flocks on the farm. Unlike other species, corn buntings do not seriously switch their minds to breeding until May/June.
Corn buntings don’t need much of a song-post - this charlock plant is about 15 cm high, but it’s higher than the surrounding crops, a prerequisite for a corn bunting song-post
Image: Nick Adams
April is still the ‘hungry gap’ when seed food is at a premium for wildlife. At Lower Pertwood they take the chance to do some supplementary feeding by giving the grain store a good clean and putting the sweepings onto one of the many wild bird covers.
May brings warmer weather and the crops really start to kick on, this means the end of the ‘hungry gap’ with food more readily available now that some plants like coltsfoot and dandelion have seeded. The corn buntings start to spread out across the farm, the flocks becoming smaller with no more than 50 birds together at a time. More song posts are popping up in the arable crops to take advantage of, these seem to help the birds hold territories across the full extent of the fields. Being organic, there is an even covering of arable plants growing below the main crop. The farm also does not weed the crops during the season, so any ground-nesting birds are safe. This delivers great nesting areas away from the edge of the fields, where nest-predation is more likely.
A male corn bunting in early June taking advantage of a sow-thistle in a rye grass/red clover mix.
Summer
June is the proper start of the corn bunting breeding season, the crops have become thick enough to hide their nests. It is the ideal time to complete a full farm corn bunting breeding survey. On many farms in the UK this would be a fairly quick process, as unfortunately there would be none present. On others, it would take a little while to pin down numbers but with a period of observation, it shouldn’t be too much of an issue.
Then there are a very few, select farms like Lower Pertwood.
Through June 2015 Nick Adams, a wildlife adviser to Pertwood Cereals (and former RSPB employee), set up and walked six survey routes covering the 1,000 or so acres of potential nesting habitat on the farm. After many hours the final total was astounding; 134 territories, nearly 2% of the UK corn bunting population on just one farm! This means that Lower Pertwood Farm is a nationally important site for corn buntings.
The attached map of the farm (see below) highlights a few interesting things as result of these surveys. Firstly, you get a clear indication for where the arable and the grassland are on the farm. Secondly, in some of the fields the males appear to be pretty much in lines. Here they are using the in-field features in place, namely the beetle banks placed in larger fields to help beneficial insects to move through the cropped land.
These beetle banks provide a great overwintering place for invertebrates like ladybirds, which come the summer provide an great organic pest control service, spreading into the crops and feed on aphids and other pests. They also make great places for corn buntings to sing from, especially on conventional farms where the crops tend to be uniform in height, and lack that all important higher song post.
Summer in full song
On most conventional farms, July sees the commencement of the cereal harvest, usually starting with winter barley. This means by the middle of August, if the weather holds, the harvest can be complete. This is not great news for corn buntings, who really need to produce two broods to sustain and increase their numbers. However, in August organic spring crops are still a little way from starting harvest. This means the corn buntings are able to produce two broods at Lower Pertwood.
As the year moves into September, corn buntings seem to disappear from the landscape and can be difficult to find. This is because they moult their wing feathers at this time of the year and being less able to fly and escape predators, they keep a low profile.
At Lower Pertwood there are many quiet areas for them to hide out in during this period. Besides the beetle banks and wild bird covers already mentioned, there are nectar and pollen mixes, areas of rough grassland, fallow fields and even areas of sacrificial crops. These sacrificial areas are left next to other features, or in areas where the crop is poor, so saving the cost of harvesting and cleaning the seed.
Find out how the corn buntings that call Lower Pertwood home cope during autumn and winter in tomorrow's post, and how the management on the farm offers them a better chance of survival.