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Around this time last year my yard was besieged with house flies. I would walk out on to the lawn (ok, more honestly, the mowed weed patch) and a hum would erupt around my feet as flies would swarm up. Needless to say it was not that appealing to be outside when the flies were in full force. I tried some pathetic attempts with DIY fly traps, disposed of dog waste rigorously, but it only resulted in a minor reduction in the fly population.
I couldn’t do much more about it without resorting to chemical warfare or importing some bacterial fly pathogen as a ‘natural’ control. Rather than imposing my will on my yard, I have chosen to follow a ‘wait and see’ policy to observe how a pest cycle changes within my yard over time. I prefer to create general habitat to support my predator populations, such as perennial plants, a constantly open water source, and regular nectar sources in the yard. I am not yet so specialized in Integrated Pest Management that I know how to attract certain pest predators, but so far this approach has worked in keeping my yard aphid free (ladybirds usually follow the arrival of any aphids). So I simply waited, watched my yard and tried to ignore the flies.
In general, I noticed the insect population increasing in quantity and diversity over time. Tiny wasps hovered amongst flowers and foliage, spider visits in our house increased, (much to my wife’s dismay), and by Fall small birds seemed to be using our yard more frequently. So it appeared that the food chain was becoming both more complex, but also more balanced. In particular I noticed one black headed visitor who seemed to be very happy in our yard snapping up bugs with acrobatic aerials and sharp clicks of the beak. As Spring rolled around she had become a fixture and was soon joined by a mate. I noticed very soon that the fly populations were drastically lower than they were last year. Curious, I did an Internet search and it didn’t take me long to discover my yard was being graced by pair of Black Phoebe flycatchers. In March they brought their chicks to our yard, and for a couple weeks our yard was the main source of food and fly catching instruction for the youngsters.
In “Edible Forest Gardens” the authors discuss functional diversity, and I watched it in play with the phoebes. I never planned to have varied fence heights in the yard, but through one thing and another there is now the 5 foot perimeter fence, the 3 foot garden fence and a decorative bamboo fence at that stands 2 feet tall. I wonder if this is one of the reasons the phoebes liked my yard so much. The tall perimeter fence provided safety from humans and dogs, yet they tended to feed mostly from the 3′ fence, and occasionally from the 2′ fence. Non-functional diversity would have been fences of different materials and construction, but of the same height, or fences that were either too high for insect catching or too low for safety. It was purely random that I managed to pull off ‘functional fence diversity’, but it was one of those happy accidents that provided part of a preferred habitat for the phoebes.
The rest of the family has since moved on, but nearly every afternoon I still have one phoebe that comes back to snack for a couple hours. Their are only a few house flies now, and every time I see her, I am grateful that we have found ways to benefit each other.
I too have a phoebe who graces my yard. Every afternoon he/she is there and now after reading your post I realize it’s the diverse heights that have drawn it to us. A swingset, a 8 ft. wall, a few wrought iron lantern holders (about 3.5 ft. tall) and a set of Adirondack chairs. I’m forever cleaning his/her droppings off my furniture and swing set, but I suppose the pros outweigh the cons.