Purple Martin Conservation Assoication
|Offering live crickets to Purple Martins that have been unable to feed because of prolonged foul weather can save their lives. A landlord is shown here placing crickets into several compartments of a martin house.|
Prolonged periods of bad weather can cause Purple Martins to die of starvation. Several days of cold, rainy, or windy weather can obliterate a colony site of martins by depriving them of their only food, airborne insects. In regions where martins are scarce, these die-offs are devastating to both the martin population and the landlord. For generations, landlords have taken a passive approach to weather-related mortality, watching helplessly as the martins at their colony site perished. If bad weather occurred during the breeding season, as it did when Hurricane Agnes struck the Northeast in 1972, both adults and nestlings died. Even the PMCA stated, in 1992, "there's not much a landlord can do when martin-killing weather strikes." But martin landlords should no longer feel helpless when it comes to the survival of their martins during bad weather. Landlords can save their martins by offering them live crickets.
The only options previously available to landlords were either to capture all the martins and bring them indoors for force-feeding (a highly intrusive, enormously time-consuming, and illegal undertaking that usually caused site abandonment by some of the martins when released) or to provide supplemental heat by placing a light bulb in an empty compartment, which would warm adjacent compartments and allow the martins to conserve energy, prolonging their lives. Ultimately, however, it is not the cold, but the lack of food that causes martins to die. Therefore, the most effective way to help martins survive prolonged bad weather is to provide them with a recognizable food source. Landlords have tried placing canned dog food or raw hamburger on the porches of their martin houses, but such efforts were rarely successful. Since martins feed exclusively on flying insects, they do not recognize a clump of meat as food. Even offering live mealworms would probably be unsuccessful unless the martins had been taught to recognize them as food prior to the bad weather. PMCA 1996 Landlord of the Year, Ed Donath, has developed a technique of training his martins, during good weather, to recognize and accept nontraditional food items (mealworms and scrambled egg; Update 4(3):2-4; and Update 6(1):6-8). While his method is ingenious and effective, it requires a substantial amount of time and effort prior to an actual emergency.
Crickets, the Grasshopper's Cousin: The key to getting martins to accept supplemental food during an emergency is to offer them an insect that resembles one of their traditional food items. Since martins are accustomed to eating live, winged insects, there are two problems involved. One is finding a source of live insects; the other is finding live insects that cannot fly away when offered! The martin's diet consists mainly of flies, wasps, beetles, butterflies, moths, dragonflies, damselflies, midges, mayflies, stinkbugs, cicadas, flying ants, and grasshoppers. None of these are commercially available in quantity, but a cousin of the grasshopper - the cricket - can be purchased in bulk at a reasonable cost and shipped overnight. (See end of article for suppliers) Crickets are similar enough to grasshoppers for the martins to recognize them as food. Several landlords have had success offering crickets to their starving martins (The Scout Report 4(1):10; and the Nature Society News 33(6):3).
How to Offer the Crickets: The best way to offer the crickets to your Purple Martins is to lower the martin house, place a few hundred crickets into several empty compartments (no nesting material for the crickets to hide in) on different sides and various levels of the house, then raise it again. Crickets become sluggish when the temperature falls to about 40 degrees, so place the cricket container outdoors for about 5 minutes prior to offering them, or in a refrigerator, to slow them down. They will be more manageable and fewer will escape. Crickets seek out dark places, so while a few crickets may jump or crawl out of the entrance holes and onto the porches, most will stay inside the compartments. Lowering the house to load it with crickets will cause the martins to fly off temporarily, but they'll soon land and find dozens of crickets crawling through compartments. The martins may be wary at first, but a martin that hasn't eaten in three days is desperate, and the sight of so many large, grasshopper-like insects crawling around should be enough of a cue to trigger feeding. If your colony site consists entirely of gourds, consider placing the crickets on an eggshell feeder (or other elevated platform) that's easily seen from the housing. To keep the crickets from escaping, cripple them by squeezing their head just enough to keep them moving, but not mobile enough to escape.
Communal Cavity Roosting: Martins have evolved a natural survival strategy for coping with emergency cold-weather conditions. This behavior is called "communal cavity roosting." When conditions become severe, such as freezing temperatures for several consecutive days, all the martins at a colony site will huddle into a single compartment or gourd to conserve body heat while waiting for the weather to break. As many as 30-40 martins might squeeze into one cavity. This dense cluster of martins generates an amazing amount of warmth, allowing them to survive for several additional days. Martins will only form a communal cavity roost prior to egg-laying. If a weather emergency strikes later in the season, martins will not, to the best of our knowledge, attempt to form a communal cavity roost.
Deciding Whether to Attempt Feeding: Whether to attempt emergency feeding while martins are communal cavity roosting is a subject that warrants special consideration. Disturbing martins that have just begun communal roosting may be counterproductive. Lowering a house might cause them to begin exiting the roost cavity, expending valuable energy. On the other hand, as with any survival strategy, communal cavity roosting isn't always successful; if the weather doesn't moderate within a couple of days, the martins eventually starve. The best approach is to closely monitor both your martins and the weather forecast. If your birds have been communal cavity roosting for more than 24 hours and there is no expected break in the weather, you have nothing to lose by intervening since your birds will probably starve to death anyway. In this case, it is recommended that the landlord offer the crickets, but without lowering the house. Either by use of a tall stepladder or a long pole with a container attached, the landlord should deposit a large "clump" of live crickets on the porch(es) just outside the entrance hole(s) to the cavities in which the martins are roosting. There are no accounts of someone attempting to feed communal, cavity-roosting, martins in this manner, but it seems worth trying. At least a few crickets should catch the attention of martins nearest the entrance, and if one or two birds eat some crickets, others might join in. To locate the roost cavity, scan the entrance holes; often, the last martin attempting to squeeze into the roost compartment may leave his or her tail sticking out. Monitor such roosts carefully, as the birds nearest the entrance are the first to die, and their bodies can block the entrance, trapping and starving the surviving birds.
When to Take Action: Do not underestimate the hardiness of Purple Martins. They are accustomed to coping with the rigors that nature poses, including short periods of foul weather. However, an average martin weighs about 50 grams and will lose 4-5 grams per day without any food (Nature Society News 33(4):6). Once a martin drops below about 37 grams (about 75% of its body weight) it begins to break down and digest its primary flight muscles, and soon dies. Therefore, since the average martin will survive for only 2&1/2 days without food (perhaps longer if communally roosting), it's best to offer an emergency feeding after only 2 days of foul, "insect-less" weather. Four conditions prevent martins from foraging by depleting the air of insects: constant temperatures below about 50 degrees, steady rain, strong winds, and dense fog. If any of these conditions (or combination thereof) persist continuously for more than about two days, some martins may die. To landlords who are monitoring their sites closely, it will be obvious that the martins are in trouble; they will sit listlessly on the martin house all day, or they will form a communal roost. They know that foraging would waste energy. If your martins have already resorted to communal cavity roosting, you might try an emergency feeding after only 24 hours.
If consistently foul weather occurs when there are young in the nest, landlords should offer an emergency feeding after just one or two days. Nestlings are not as hardy as their parents, and will die much sooner when deprived of food. If martins suffer reproductive failure - for any reason - they will abandon their breeding site. Landlords should offer smaller crickets when parents have tiny young to feed. Do not place a large number of crickets directly into compartments with nestlings. Rather, load-up empty compartments, allowing the crickets to disperse throughout the house.
Temporarily "converting" your martin house into a cricket feeder could save your colony site, especially if it's located in an area where martins are scarce, or an area which has become marginally acceptable habitat that would not likely be recolonized if abandoned. Old colony sites in urbanized locations (that were rural when the colony was established) are one example of such a site. While martins loyally return to the area even though the character of the area has changed, if the nesting tradition is broken for just one breeding season, the colony site is usually lost forever. Many small colonies in the Greater Pittsburgh area of southwestern PA were wiped out when Hurricane Agnes stalled over Pennsylvania in mid-June of 1972, causing three weeks of constant rain. All the young and most of the adults died. The destruction of martin colonies was so severe and widespread during this storm, that even now, 27 years later, martins are scarce or nonexistent in this area. It is interesting to speculate what might have happened if landlords back then had supplied emergency cricket feedings. How many people could have saved their colony sites?
Messin' with Mother Nature?: Some might argue that emergency feeding is artificially tampering with the normal balance of nature. After all, haven't spring die-offs been occurring for eons? Aren't they a natural biological control of the population and a way of weeding out unfit genes? Perhaps, but the actions of mankind have already affected the martin population in such negative ways that some positive, corrective tinkering is justified. For example, if man hadn't introduced the European Starling and House Sparrow, martins would more easily recolonize areas that experience massive weather die-offs. As it is, these exotic pests are quick to move into an unoccupied martin house and prevent or hinder recolonization, causing an artificially low density of martins in some areas. Emergency feeding of Purple Martins may turn out to be an effective wildlife management tool in these regions.
Cricket Ordering Information: Crickets can be ordered year-round from Fluker Farms (1-800-735-8537). 1000 live, six week-old crickets, about 1 inch long, will cost $19.95 plus shipping. They can be shipped Airborne Express overnight on weekdays for about $10.00. (Orders must be placed before noon to get overnight delivery.) Crickets can be kept in a glass aquarium with a cover and fed dog food and fruit. Consider ordering smaller crickets if the weather emergency occurs when parents have young to feed. Four week-old crickets are 1/2 inch long and are the same price. Even very small "pinhead" crickets can be purchased in bulk; consider these if the martins have tiny young in the nest. Crickets can also be purchased at bait shops or retail pet stores, but they will usually be more expensive. Ordering several thousand crickets will see your martins through several days of bad weather.
This article was inspired by a letter from Dave Franzer of St. Peters, MO, who was one of the first to successfully use this cricket-feeding technique. I would like to dedicate this article to all those landlords in the Pennsylvania-Ohio-West Virginia region who lost their martins to Hurricane Agnes in June of 1972.
Copyright 1999by Purple Martin Conservation Association. All Rights Reserved.
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