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When is the right time to mow hay fields?

Every year about his time, I feel sadness for the many birds and small mammals killed by haying. I will begin this discussion by stating, I know there are many and varied reasons why fields are cut, and I respect that.

Mowing of hay fields is a necessary and important part of agricultural practices. We forget this field of lush grass and forbs is actually an agricultural crop. Unlike most crops in Ontario, up to three harvests can occur in a single growing season! The only question I have is, does the cutting have to occur during the height of the breeding season of these grassland birds, at a time when most of them are in rapid and dangerous decline?

Haying seasons are classified as early, middle or late. The early and middle haying in Ontario takes place from mid-May to mid-July. This, unfortunately, coincides with most of the nesting season for all grassland species of birds. According to the Ontario Soils and Crop Association, early and middle haying results in the loss of over 90 percent of all grassland bird nests. This comes at a time when the 30 or so grassland species which nest in our area are in decline. Bobolinks are down by 88 percent over the past 40 years, Eastern Meadowlarks, Savannah Sparrows and Barn Swallows are down nearly 70 percent, and Loggerhead Shrikes and Henslow’s Sparrows, once widespread, are now on the edge of extinction in Ontario.

So what can one do? The obvious answer is to either not mow during the breeding season or to mow, keeping the behaviour of the birds in mind.

Mowing too early in the season, surprisingly, may not be the answer, as the resulting cut fields may not be suitable habitats when the birds are setting up territories, as the grass is too short. Knowing something about the birds, how they behave and where they like to nest, can allow both nesting and mowing to coexist.

Equally important is knowing what birds are sharing the fields and which ones might be of most concern. Again, the Ontario Soils and Crop Association has an excellent publication available online, called Farming With Grassland Birds. Now before I go on, I am not a farmer and don’t profess to understand the intricacies of hay and forage production, but I found this publication very enlightening, and it made sense to a layperson like myself.

Using the behaviour of the birds to help decide how to manage fields is paramount, for their consideration. For example, many grassland birds prefer not to nest in smaller fields or fields closely bordered by forest edges. They will move to the middle of such fields if possible. The response from the farmer could be to mow the outer rows of a field in June and early July, but the middle can be mowed after July 15th, when the birds are done nesting. Many grassland birds seldom nest in fields smaller than 4 hectares (10 acres) or with a minimum width of less than 200 metres. So, if the fields are small and rectangular, the impact of mowing may be minimal for most endangered species.

Did you know alfalfa-dominated fields are less desirable to grassland nesting species? And meadowlarks will likely renest, but Bobolinks won’t?

The literature doesn’t seem to address another solution I think could help. Can the mowers be set higher, so at least some cover is left for the birds and small mammals nesting in the fields?

Currently, mowers cut down almost to the ground surface, so many nests are trampled by the wheels of the tractors, or they may be exposed to the elements. The young die of exposure or, more importantly, they are exposed to foraging predators, such as gulls, foxes, coyotes, raccoons and others.

There is much more to say on the subject, and I would encourage anyone with an interest in helping our grassland birds to read Farming With Grassland Birds, so I will leave it there for now.

Geoff Carpentier is a published author, ecotour guide and environmental consultant. Visit Geoff on LinkedIn and Facebook.

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