It rains in a rainforest.

the usual fog and rain rolling in amongst the 'ohi'a canopy

As the title suggests, the rain certainly falls in Hakalau Forest NWR, where I have done all my field work in Hawai'i. If you read my first post you may remember me mentioning this quite a bit. In fact, Hakalau gets 250 inches of rain every year in parts of the refuge. That is close to 21 feet of rain every year (which is more than two basketball goals stacked pole to rim for all you sports fans). For reference, we only get a little over 20 inches of rain here in Flagstaff, AZ where I currently live. Hawai'i is in the middle of the Pacific Ocean, with nothing between it and the coast of North America except ocean. The prevailing winds (the trade winds) blow from east to west, from the continent across the ocean and right over Hawai'i. There is a lot of moisture in that stretch of 1500-2000 miles or so, and the air picks it all up. Once the winds reach Hawai'i, they suddenly slam into the side of a 14,000 foot mountain, and all that moisture condenses and falls down. Usually on me, and making things very wet for us field biologists. Lots of clothing layers, rubber boots, wet vegetation that you have to walk through and sit down in, and a distinct lack of sunshine. However, at the end of the day, we get to back to our field house, put on some dry clothes, and warm up next to the gas powered range top while cooking dinner. The birds that we study on the other, well, they're stuck out in it.

sunrise over the barn at Pua Akala, Hakalau NWR, before the rain settles in for the day

You may wonder how these birds deal with all this rain and cool temperatures. I mean, they have feathers and all, but how warm are those really? Well, birds have a special gland on their back which secretes a type of oil. You may have seen birds rubbing their beak through their feathers and making sure each one was lined up right, as if they were readying to go on a live TV show. What they are actually doing is rubbing oil from this gland all over their feathers and essentially waterproofing them. They are also making sure each feather is lined up correctly to leave no gaps. In this way, they always have their raincoat ready, and don't get quite as wet even when out in the rain.

Cloudy days at the Pua Akala site, Hakalau Forest NWR

Although the rain doesn't seem to decrease the birds' activity too much (they are still singing and flying about in the rain), it probably does hinder them a bit in other ways. The majority of the active nests we were monitor at Hakalau actually fail during periods of prolonged rain, and most of that seemed to be parents abandoning their nests. Birds with both eggs and chicks left their nests, leaving eggs to get too cold or chicks to starve. This sounds harsh, but most likely it means that the birds have a difficult time getting enough food resources to both care for eggs or chicks and keep themselves healthy in a cool and damp environment. These birds have long life spans (at least compared with other small birds!) and a long breeding season (6-8 months compared with 3-4 months here in North America), so time is on their side. If they have to give up on a nest with babies in it, at least they will have plenty of time to try again without causing themselves to become unhealthy. It seems unlikely that there simply isn't enough food present; instead those food resources may have simply been a little harder to come by in the rain. Also, the parents use more energy staying warm, and therefore must find and eat more food themselves. However, as soon it becomes sunny (or rather, just doesn't rain that much) for a few days, all of the birds begin rebuilding nests to start all over again. They don't give up that easily, so neither should us field biologists!

But rain makes the rainbows at our field house!

What mountain range is this? Oh yea its just one mountain - Mauna Kea. When a big storm rains in Hakalau, it usually means snow on the mountain summits. And yes, it does snow quite a bit in Hawai'i.