In and Out of Harm's Way

How I prefer to see western yellow-bellied racers in the Dipper farmyard - out of harm's way.
June 2, 2009   

On May 25, I was mowing the orchard with a big walk-behind mower. The coyote brush was starting to take over and this mower is powerful enough to cut down young shrubs as tall as 3 feet. On a return path of my back-and-forth mowing pattern, I found an injured western yellow-bellied racer on the edge of the tall grass. Sadly, I realized I had probably hit it with the mower despite looking ahead and mowing in a way that gives wildlife the best chance to flee from the noisy machine. I set the injured snake in an area that was far away from my mowing duties. It was probably going to be dinner for a coyote or fox that night.

Protecting Wildlife While Mowing

--- Nest of baby bunnies found by Miriam Sachs Martin while moving tarps. ---

We mow to control weeds and to reduce fire hazards around our home and ranch buildings. But the mowed fields can also be the home of wildlife, so how do you protect wildlife while mowing? Animals that may be harmed while mowing, weed-whipping, brushcutting or discing grasslands or weed stands are: ground-nesting birds, snakes, frogs, toads, turtles, lizards, salamanders, rodents, and rabbits. Even small fawns may be hiding in the grass, and if they are following their mama's orders, they won't budge until she says so. If you want to keep the wildlife while modifying the plant environment, here are some tips to consider while mowing.

PRE-CHECK - Walk the line, walk the field. It's a good idea to start by walking across your work area to remove mowing hazards such as rocks, branches, and badminton rackets anyway. This is also the time to check for wildlife and develop a response plan. Inspect your work area before you turn on the equipment - noisy engines scare some animals into hunkering down and hiding in place.

--- Southern alligator lizards are especially slow, perhaps it's that long tail. ---

When mowing long, straight lines with a big tractors such as for a fire break along a road, some folks have one person walk in front of the tractor during the whole mowing operation to flush any wildlife. For larger fields, you don't have to walk the entire area - just crossing the area several times may flush visiting critters away. You can keep the snakes and lizards rolling along by walking behind them until they are well outside the work area and unlikely to turn around and come back. Turtles may appreciate a lift. Fossorial animals (= digging) may dash into a burrow and stay there until the commotion is over.

California quails, grasshopper sparrows, and western meadowlarks are common birds that could be nesting on the ground and are easy to flush. Detecting and avoiding their eggs or nestlings can be more difficult. Look for birds singing repeatedly at the same location to claim territory around their nests. If you notice birds that flush from the ground, act defensively, feign broken wings or fly into the grass with nesting material or food, it is likely a nest is present. Some adult birds chirp repeatedly as you approach a nest. High pitched calls may be nestlings. Careful, quiet observation may help you discern where the birds are flying in and out of the vegetation and where the nest is generally located. Some birds pull strands of surrounding grass over the top of their nests as camouflage; train yourself to look for patterns of bent-over grass as possible nest locations. Stay about 15 feet away from the probable nest location and treat the weeds with less disruptive methods (spot spraying of herbicides or handpulling), or mow this area later in the season, if possible. Remember that many birds nest more than one time in the summer.

TIMING - Mow early or late, or carefully in between, and know your grassland critters and when they might be seen.

One way to avoid striking wildlife with your mowing implement is to delay mowing until after midsummer when nesting is done or slowing down. Unfortunately, you may not be able to wait since this is often too late if you want to prevent annual weeds from going to seed. Furthermore, annual grasses should be mowed while they are still green to prevent hot mowing equipment from igniting a fire in dry, brown grass. Another precaution in fire hazard areas is to mow before 10 AM during the summer when moisture of vegetation is higher and less likely to ignite. See the mowing, string trimmer and other short videos at the CAL FIRE website for excellent safety tips on mowing during the fire season.

You can also adjust your timing by the weather or time of day. Animals are less likely to be moving about in the grass on a cool or an especially hot day, but those that are resting in the grass are slower to retreat, so be especially alert. The same holds true for the cool and hot parts of the day. Reptiles and amphibians use the sun to modify their body temperature, so you are less likely to come across them in the morning, however, carefully check sunny spots on a cool morning where reptiles may be warming up for the day. Birds are happy and singing in the morning, so that is a good time to precheck for them.

--- Gopher snake in the grass. ---

MOWING PATTERNS - Mow outwards and pause at edges. Circling inwards is a common mowing pattern in urban yards, however, in fields, this may force wildlife to retreat into the shrinking patch of tall grass in the center where they are most susceptible to being hit as you finish up. You can change your mowing pattern so that you are mowing inside-out or in consecutive rows rather than circling inwards. See mowing diagrams of inside-out and consecutive rows at this Indiana Division of Fish and Wildlife website.

For mowing inside-out, make the first cuts through the middle of the work area and progressively circle towards the outside edges. This allows wildlife to move outwards away from the noise and cutting blades. This requires a tight turning radius for the first few passes so that you may need to reverse and forward large-wheeled equipment several times on the first few turns. You will also be initially throwing cut material onto your second mowing pathway.

Mowing in consecutive rows can "push" the wildlife to the edges of the mowed area. It requires a tight radius at every turn, so is more appropriate for unwheeled equipment like string trimmers and brushcutters.

Consider leaving edges along fences and rocky areas to last when you are mowing. This not only leaves these areas as retreat and hiding places for animals, but because rocks and fences are the locations where you are most likely to ding and dull your cutting blades or strings, you have less maintenance if you end the mowing session there. Some people will mow part of a field one day and leave interior or edge areas for mowing a few days later to allow wildlife to move out.

On very large fields, another strategy is to cut one-third of the field each year and leave the rest to wildlife, if that meets your other mowing goals. In general, leaving some uncut areas on the property will benefit wildlife.

EQUIPMENT TYPES & MODIFICATIONS - Mow up, look down. For equipment that allows adjustment of the mowing deck, set the mowing height 4 or more inches above the ground, if that otherwise meets your mowing goals. Mowing several inches above the ground may avoid nests and small animals, and I find this works fine to stop mustard plants that have started to flower. However, mowing several inches high may not sufficiently set back some weeds like thistles which will resprout and seed, and thus require subsequent summer cutting and another round of potential disturbance.

Brushcutters and string trimmers allow the operator greater visibility and quicker response time if wildlife is observed while mowing. They also allow greater flexibility in momentarily adjusting height and the direction of the cutting path and are faster to turn off. Operators tend to cut more slowly when using these unwheeled cutting implements, thus they give wildlife a longer time to escape the commotion. These hand-carried implements can be more time consuming and tedious to operate over large areas. They are better for small areas or to trim out edges or especially sensitive areas near water or brush. Invest in a good harness for brushcutters. Your comfort will allow you to have greater maneuverability and cover more area in potential wildlife habitat before you fatigue.

--- Joe Mackessy uses a brushcutter with a harness and bicycle handles
that give him greater control and comfort so he can work carefully and longer. ---

Wheeled mowers and tractor-pulled brushogs are less flexible in turning, but they can be raised to a regular higher cut. These large mowers can be modified with flushing bars or leading edges on the decks to flush wildlife in front of the equipment or prevent small animals from being sucked in under the deck. Slow down the pace of these larger pieces of wheeled equipment to give wildlife time to escape.

EXPERIENCE - I like to compare mowing to food preparation. With time, you accumulate more and better quality cutting tools and are able to match the right tool for the right job. You also become more aware of avoiding living things (like your fingers or bunnies). Neighbors who share recipes may also have good tips on mowing.

It is difficult to mow in the spring and summer in the country, meet your weed control and fire safety goals, and completely avoid wildlife. These tips should help you thoughtfully seek ways to lessen the possible conflicts. The most important tip is to SLOW DOWN - it gives you time to observe, gives wildlife time to retreat, and as always, be safe.

The safe mowing chant:

• Walk the line, walk the field.
• Mow early or late, or carefully in between, and know your grassland critters and when they might be seen.
• Mow outwards and pause at edges.
• Mow up, look down.
• Slow down.

Thanks to Heather, Miriam, Stan and others for their advice on this topic. If you have any other suggestions, especially innovative mowing patterns, please comment on this posting.

SEE ALSO:

• Cornell Labs for photos, audio recordings of calls and descriptions of ground-nesting birds.
  
• Managing Pastures and Hayfields for Wildlife, University of Arkansas, Cooperative Extension Service - includes information about flushing bars on mowing decks
  
• Some of this information was presented in a workshop by the San Francisco Bay Bird Observatory
  

Mowing Thistles

Mowing is a strategy to stop a large stand of thistles from producing viable seed. It requires good timing and usually needs to be repeated several times during the spring/summer season.

If you haven't already eliminated the thistles in your target area, it's probably time to switch strategies. The thistle plants are bolting - sending up straight, tall stems from the center of their rosettes (ground-bound circle of leaves), and thorny buds are forming at the top of the bolted stem. These are the flower buds.

<--- bolting purple starthistle plant ---

On the Italian thistle, some of these buds are starting to open and reveal the numerous purple flower petals (top photo). I will be mentioning Italian thistles often in this post because they are the first thistles to bolt and are currently flowering at the Dipper Ranch (2200-foot elevation) in our region.

Under Thistle Logic, I described how to tell the different thistles by the shape and markings on their rosette leaves. Now you can also sort the thistles by their flowering characteristics. Italian thistles have "decurrent" stems - the spiny edges of each pair of opposite leaves continue down each side of the stem like long fins or spiny ruffles. The Italian thistle flower buds are clustered together at the tip of the stem and they usually are 1/2 to 7/8" wide including the spines , noticeably narrower than other thistles common in the Santa Cruz Mountains.

Timing: Once an annual plant starts to bolt, it is determined to flower and produce seed. By timing your mowing correctly, you can use this inclination to your advantage. Changes in the chemicals circulating in the plant at the time of bolting cause the growing tip in the center of the rosette to produce elongating cells. Once the stem reaches approximately knee height in the Italian thistle, the growing tip switches to producing flower buds. Two to five flower buds form at each stem tip. These quickly swell into their spiny threat. The phyllaries (overlapping leaves covering the flower bud) open and the purple petals reveal themselves, although the flower heads on the Italian thistle never open into a broad face.

<--- decurrent stems of the Italian thistle ---

Thistles are pollinated by insects. You might see honeybees, native bees, flies, beetles and ants visiting the thistle flowers and thus spreading the pollen from flower to flower to create fertilized seeds. The insects may also be there to eat the seeds or lay their eggs among the thistle seed larder.

Each individual Italian thistle flower head is actually made up of about 14 small flowers bunched together. That means that each Italian thistle plant can produce hundreds of seeds. All that thistle bounty is from one original seed, so it's important to stop the flowers from developing viable seed.

<--- honeybee on milk thistle ---

Mowing down the thistle stems will stop the development of the flowers at their tips. Wait to mow until the plant has made a serious investment in stem growth - when the stem is about 1/2 its ultimate height or up until the time when the flower buds start to swell . If you wait until the flower buds have opened, some of the flowers may have already become fertilized; even after being severed from the nourishment of the live plant, there may be enough energy left in the stem and bud for the seed to continue to mature and become viable.

Repeat Mowing: The thistle plant, however, is still determined to flower and seed, so it will probably send up another or several more bolting stems in the next few weeks. Keep an eye on the resprouting and mow the thistles again when the stems are several inches high yet the flower buds are not open. Depending on your regional climate, the wet/warm periods of the current season, and the species of thistle, you may have to mow one to four more times in the summer.

<--- Bolting Italian thistles. This stand has no open flowers and is ready to mow. ---

Sometimes, plants will react to mowing by sending up very short stems and the new flowers will be so low to the ground, you won't be able to mow them with typical mowing equipment. Then you are at risk of letting the plants go to seed. This is a bad situation and the best way to avoid it is to make sure you don't mow the plant too early - make sure the plant has already sent up several inches of bolting stem. Each time you chop off a considerable bulk of the plant in the stem, you are removing much of its resources. Repeated mowing should eventually deplete the plant of energy. In fertile soils and with mild, rainy summers, the thistles may keep resprouting until the weather and day length finally trigger the end their annual lives.

In poor soils, or dry conditions, the thistles may grow to a shorter stature and produce smaller flowers sooner. The bolting of the stem, and formation and swelling of the flower buds will still follow a predictable pattern that you can track to determine the right time to mow.

--- Weevils mating on the leaves of an Italian thistle at the Dipper Ranch. These may be thistle head weevils (Rhinocyllus concicus), an introduced biocontrol insect that unfortunately may also attack native thistles. --->

Individual plants within a stand of thistles can grow at different rates. Try to time your mowing to get most of the flower heads at the right stage or err a little bit on the early side so fewer flowers are likely to go to seed. You can walk through a thistle stand before mowing and pull out the plants with opened flowers or cut off the ripe flowerheads. Put these into a container for disposal. To avoid throwing more material into the landfill, I usually stockpile mature/pulled thistle plants in the corral where the cattle eat and stomp on them. Even though some may continue to develop to mature seeds, if they germinate next year, they are likely to get beaten by the cattle again, or at least I can attack them all at once in one spot.

In conclusion, carefully time mowing of thistles and expect to repeat it several times in the summer. Soon, I will describe techniques to avoid harming wildlife while mowing, sheet mulching and how to tell if a seed is ripe.

See also:
Italian thistle, Carduus pycnocephalus
Purple starthistle, Centaurea calcitrapa
Milk thistle, Silybum marianum

• Weeds of California and Other Western States, Joseph M. Ditomaso, Evelyn A. Healy, 2007, University of California, Division of Agriculture and Natural Resources.
  

--- This flat field in Pasture 1 was probably cultivated in the past, but now hosts a big stand of milk thistles. The crew mows it with a tractor. We call it "the deer golf-tee". --->