To Slash, Burn or Plant?

August 23, 2013

Nature Notes by Bill Dunson


How do you maintain a grassland prairie or meadow?  In most eastern locations these would return to a forested condition naturally by succession unless some disturbance such as mowing or burning intervened.  In wildlife refuges it is desirable to maintain a high diversity of habitat to maximize animal species diversity.  On our farm we are attempting to maintain the historic areas of pasture/hayfields by a combination of mowing  plus burning on slopes too steep to cut.  These steep areas that were pastures were formerly maintained by grazing, but cattle introduce a whole new set of problems related to overgrazing, weeds and nutrient pollution.

Our approach is to mow about 2/3rds of the grasslands, and hold about 1/3rd in uncut parcels planted with native grasses and flowers which are not mowed but may be occasionally burned.  The steep marginal areas are burned about every two years.  The crucial aspect of mowing for hay is timing and frequency.  It is common to read that one should mow fields late in the summer to avoid disturbance of breeding birds.  This is problematic in that there is then little time for the fields to re-grow before the winter, so little food and cover are provided for wildlife.  It also does not stimulate the growth of dormant summer grasses and forbs which are suppressed by the predominant early spring exotic grasses such as fescue.  So we mow the fields once only in mid June, allowing time for birds to re-nest, and for re-growth of the fields prior to frost.

Some of our target bird species are migratory bobolinks which stop in the spring and fall to feed; we hope they will nest here some day.  A grassland breeding bird of special interest is the meadowlark which requires fairly short grass cover.  We also have savannah sparrows which breed and blue grosbeaks which seem to prefer the edges of grasslands with some trees.  Bluebirds and willow flycatchers also thrive in the edges of grassland with shrubs and trees.  Wintering white crowned and swamp sparrows enjoy the dense grasslands and brushy and wet edges.

Our fields contain abundant milkweeds which provide both nectar for many insects and larval food for monarchs.  How does our mowing schedule impact them?  Well at first you might think it would be very deleterious to mow the milkweeds in mid June.  However by this time the milkweed leaves are quite tough and probably not very suitable for monarch caterpillars.  So by cutting in mid June, this results in lots of young tender leaves available for monarch caterpillars by mid August and early September.

Once you begin to manage land to enhance wildlife you quickly begin to realize how complex the ecology of even a small piece of land can be.  But by focusing on the specific needs of key species and experimenting with different approaches, you can often achieve success in providing prime habitat for chosen species.  You will also find that some species need habitat which you cannot provide without additional changes you may not be willing to make.  For example our neighbor’s cow pasture has breeding grasshopper sparrows which we cannot attract since apparently we do not have sufficient bare ground without the disturbance of cow hooves.  This approach of defining what species you want to attract and maximizing the potential of your habitat in providing cover, food for young and adults, water, and breeding conditions can be successfully applied to even a small yard.

Bill Dunson, Englewood, FL, and Galax, VA

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

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