Weather and Martins

Current Weather Conditions

Some Weather Effects on Purple Martins

Martins have developed a survival strategy for coping with emergency cold-weather conditions that can occur in the spring, shortly after they have arrived at their breeding grounds or during migration. This behavior is called “communal cavity roosting.” When conditions become severe, such as snow, sleet and freezing temperatures for several consecutive days, all the martins at a colony site will pack themselves 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 for the duration of the cold-weather spell! This dense cluster of martins generates an amazing amount of warmth, allowing them to conserve energy and survive for several additional days.

But landlords should pay close attention to their colony sites during these stressful conditions, because communal cavity roosts can sometimes result in the death of all the martins in the cavity roost, even after the weather breaks. Here’s how: The last martins to pack into the cavity roost end up near the entrance hole. (Their tails will often be sticking out.) They are the most exposed to the cold and wind, and usually the first to die if severe conditions persist. If these martins near the entrance hole do die, they often entomb their surviving roost-mates by blocking the entrance/exit hole. The surviving martins are thus prevented from exiting the cavity to resume foraging when/if the weather breaks, and they starve to death. In other words, the bodies of the dead martins can block the entrance/exit hole and literally entomb their still living comrades – burying them alive!

If a landlord closely monitors the site (with binoculars) they can detect these communal cavity roosts and take action if needed (i.e., remove the dead birds). Tails sticking out of the entrance hole will often be a sign that a roost has formed in a cavity. Tree Swallows will sometimes join cavity roosts with martins.  Other species, such as wrens and bluebirds will also form their own roosts under severe conditions.

Of course, landlords can feed their martins crickets or mealworms during very cold weather, before they resort to communal cavity roosting, which is usually a last-ditch effort to survive. Go to and scroll down to management for a few articles on emergency feeding. Thankfully, the severe cold-weather conditions which lead to communal cavity roosting only occur about once every 10-20 years (my guess) in any given area, and the occurrence of such conditions is more prevalent in the northern parts of their breeding range.

Ken Kostka

Emergency Feeding Martins by Louise Chambers PMCA

Some very important information  noted from the PMCA FORUM/UPDATE

Here are several excerpts about feeding from two articles from the Update. Both articles are available as pdfs in the Basics for the start of the season sticky. If you haven’t read them, or if you are not having success feeding, or are wondering how to feed – please read them both.

Four types of weather conditions can adversely affect insect availability, causing Purple Martins to starve: constant temperatures below 50 degrees, steady rain or drizzle, strong winds, and dense fog. The average martin will survive for about 4-5 days without food, but will become weakened after 2-3 days, so it is best to begin feeding before they become too weak to fly. Feeding is even more beneficial when martins have nestlings to feed, as nestlings may only survive one or two days without food. [NOTE: Ours are out feeding now, in the 40s, but it is sunny and calm. Add wind, drizzle, or fog and insects can be much harder to find in the 40s, 50s, and 60s]

How much to feed: This is so you know to order and offer enough food. Always keep feeding until the martins are satisfied – that is, don’t cut them off after you calculate they’ve had 30-40 crickets each. Keep feeding! The amounts listed below may not be enough during extra cold weather.
20 giant meal worms (17.4 grams) per bird per day

Approximately 32 crickets (17.4 grams) per bird per day

6 large eggs will feed 10-12 martins for 1 day

In addition to knowing what weather conditions place a strain on martins, landlords can look at the birds themselves for cues on when to feed. Listless martins that spend the entire day at the colony site are obviously not feeding. Watch perched birds for signs of drooping wings—a sign that the martin’s system is beginning to break down and digest its primary flight muscles. In extremely cold temperatures, martins will begin communal roosting, where a dozen or more birds will crowd into one compartment or gourd. Clustering together conserves body heat, allowing martins to save energy. While this is a beneficial adaptation, it is a sign that martins are in “survival mode.” [NOTE: Be sure to lower and check every cavity when martins leave to feed after bad weather. Try to check all entrances daily, with a walk around and binoculars. If a martin dies and blocks the entrance, all the birds trapped behind it will die – so check for dead birds]

Heat Can Help: Jeff Wilcut, in southern Iowa, reported that prevailing winds resulted in mass starvation at many colonies one spring. In one day, Jeff found 45 of 60 birds dead. He reported that another martin landlord in IA lost only 10 of 50 birds, possibly because he installed a 60-watt light bulb in a spare compartment of his martin house. Providing warmth could extend a martin’s life by a day or so, by allowing it to conserve its limited energy. Landlords are also reporting that hand warmers (available from sport or hunting supply stores) are a good alternative to light bulb heat. The nontoxic, odorless warmers hold their heat for up to 24 hours.

Larry Melcher from the PMCA produced this feeding video in 2009. Have a look!

For more information, see Purple Martin Update articles [Many of these are in the Archives, but reading the two in the sticky Basics on this page covers most information well]:

  • “Emergency Foul-weather Feeding or Martins: Crickets Could Save Your Colony Site!” Vol. 9(1) pgs. 27-28
  • “Cricket Tossing: A New Emergency Feeding Technique for Purple Martins” Vol. 9(4) pgs. 26-28
  • “Supplemental Feeding Reduces May 2002 Weather Deaths of
    Purple Martins” Vol. 11(3) pgs. 1, 24-27
  • “Saving a New Jersey Purple Martin Colony Using Supplemental Feeding” Vol. 12(3) pgs. 2-7
  • “A Basic Guide to Feeding Martins” Vol. 13(2) pgs. 22-23

There is a sticky post on this page with links to two feeding videos by Larry Melcher and Tim (bruntdog). They are very helpful so check them out. You can get a good DVD on feeding, produced by NJ landlord Tim Shaheen, in the Martin Market Place—see Emergency Feeding Video/DVD

Don’t try once & give up – best opportunity to get birds started may be after 2-3 days without food. Order crickets and mealworms online, it’s a lot cheaper than pet stores. Try eggs while waiting for insects to arrive, but if eggs fail, don’t use that rational for not ordering insects. For those that want to try, this is a very good time to train their birds to take emergency food, and to save some lives. Get some hand warmers, light bulbs, etc into housing to help the martins conserve their energy a bit longer. Foam nest trays and nest material help too, so get some shavings, pine straw, etc into all cavities too.

Check out the current weather conditions for your area. You just never know when the martins will need your assistance in case the weather changes for the worse.

Summer Emergency Feeding During Very Hot/cool Conditions

Ken and Louise’s articles on feeding martins during very cold conditions are excellent pieces of information to note when adult martins are in trouble and unable to feed in the early Spring.

Sometimes very young martins-nestlings are not fed due to a lack of insects during cool summer months or very extreme hot conditions. This is most apparent perhaps when the young birds fall from their nests or adults  are away for long periods of time and do not provide adequate food for them due to the lack of insects for an extended period of time.

If your martins are trained to feed during the Spring cold conditions, try feeding them during the adverse summer conditions. Martins will quickly return flipped food to their young thus providing them with the needed nutrition to get them through this stressful time. Although not strongly endorsed by many, don’t hesitate to feed your martins during good weather conditions. Some of them will take this supplemental food and encourage other martins by their behaviour in the colony  to accept the random egg or cricket. It is highly encouraged to  train your martins for just that day when they will really need it!