Why do some trees get so tall?

published 12/31/2019 in the York Weekly, Foster’s Daily, the Portsmouth Herald and online on seacoastonline.com

I was just out visiting my son who lives on the coast of Northern California, the land of tall trees, the coast redwoods.  Coast redwoods (these are the state tree of California) are the tallest trees on Earth. I was thinking about our New England tall tree, the white pine (the state tree of Maine), and wondering whether they ever had a chance of growing as tall as the coast redwood.

Navarro River Redwood State Park near Mendocino California

There are a large number of factors that determine how and why a tree grows tall: genetics, environment, age.  The primary reason for a tree to grow as tall as it can is to beat surrounding trees to the sun. White pines and coast redwoods are great at this and will dominate a forest if they can get to the sun first.  White pines typically grow to about 150 feet tall (however pre-colonial white pines have been estimated to reach heights of at least 230 feet) while coast redwoods grow twice as tall-300 feet and taller (the tallest tree in the world is a 379 foot tall coast redwood named Hyperion).  How do they do it?

The two problems that have to be overcome to grow super tall are water and wind.  Coast redwoods tend to occupy sheltered valleys where they are protected from wind.  Like all trees they need to somehow distribute water to all parts of the tree. The long-held dogma of how this is accomplished is that groundwater enters the roots and is pulled upward through the tree by water evaporating from pores in the leaves.  Water is sticky, so as one water molecule evaporates from a pore in a leaf it pulls another water molecule up after it. The taller a tree grows the more difficult it is to get water up to the topmost leaves-gravity becomes a major drag. If those leaves can’t get enough water photosynthesis and growth start to slow.   

However this upward flow of water  isn’t the whole story. It turns out many trees can also absorb water into their leaves and move it downward towards the roots. There has to be water vapor in the atmosphere for this to be a useful adaptation.  Coast redwoods live in the fog belt, their needle-like leaves are almost constantly bathed in fog. Studies by the National Park Service found that some coast redwoods obtain 40% of their water from fog, not their roots!   And, according to a study on coast redwoods published in Functional Ecology (“Pushing the limits to tree height: could foliar water storage compensate for hydraulic constraints in Sequoia sempervirens?” published 2014 by H. Roaki et al) the pinnacle (topmost) leaves of the tallest growing coast redwoods stored water better than trees that didn’t grow as tall. So, tall-growing coast redwoods can take advantage of all that ambient water in the surrounding fog and both store and use it for growth.

Another factor in height is age-it takes time to acquire all of that biomass.  White pines easily live a couple hundred years-the oldest known specimens are over 400 years old.  Coast redwoods, on the other hand, are among the oldest living things on Earth-they can live for more than 2,000 years (the oldest living coast redwood is 2,200 years old).   Hyperion, the tallest tree on Earth, a baby by coast redwood standards at somewhere between 600 and 800 years old has still had a remarkably long life.

Redwood stumps provide nutrients for new growth. Here some sorrel grows at the base of a stump

So, while our East Coast white pines probably couldn’t ever grow as tall as coast redwoods, -conditions and adaptations aren’t quite right-one similarity between these two species is how it feels to walk into a white pine or a coast redwood forest.  There is a cathedral like quality to these forests, they are quiet and dark. The filtered sunlight adds to their majesty, illuminating the mist in much the same way that light falls through the stained glass of a human-made cathedral and illuminates the dust motes floating through the air.   These forests we walk through today are largely young trees. Just imagine the grandeur of a pre-colonial forest, fully mature white pines or coast redwoods reaching towards the stars.


published Dec 25, 2019 the York Weekly, Portsmouth Herald, Foster’s Daily and seacoastonline.com

I think if you ask any New Englander to name the top three birds at their feeder, the chickadee would be on everyone’s list. I also think that of any of the common bird calls in our forest, the chickadee’s is the one most of us could easily identify. These tiny, round birds with a black cap and bib that contrasts with its white cheeks are found all over the northern parts of the United States and up into the middle of Canada.

black-capped chickadee

When not living in the suburbs you can find them in deciduous and mixed forest, almost any kind of open woodlands, as well as thickets. When we clear forests for agriculture or development, we are increasing the amount of forest edge – a habitat type that chickadees love (unlike something like an ovenbird that requires deep woods for nesting).

The black-capped chickadee (Poecile atricapillus) is one of seven species of chickadees found in the United States. They all have similar body shapes with sometimes subtle differences in color or streaking on their heads. For example, the boreal chickadee (the other New England chickadee) has a brown cap and cinnamon flanks and a more northerly range, preferring the boreal forests of Canada and the mountains of New England.

Chickadees probably do so well with humans due to their flexibility and curiosity. They are highly social birds that are quick to explore new environments and take advantage of resources (they will usually be the first bird to use a new feeder). According to the Cornell Lab of Ornithology, one study found that “every autumn black-capped chickadees allow brain neurons containing old information to die, replacing them with new neurons so they can adapt to changes in their social flocks and environment even with their tiny brains.” They really do have tiny brains, which makes their ability to memorize that much more remarkable. They often hide food for later use and can remember thousands of hiding places!

Try listening to their calls. They actually have a very complex language, much more than the obvious chickadee-dee-dee. They can communicate information about other flocks, predators and foraging information. For example, they add ”-dees” to their chickadee call to indicate higher threat levels.

From the number that show up at my feeder every day one, wouldn’t know that we are in the middle of a mass extinction of birds. A recent Science Magazine article recently reported that there has been a 29% decline in birds in the United States over the past 50 years (that’s almost 3 billion fewer birds on the North American continent today compared to 1970!). While chickadees aren’t considered endangered, or even threatened at this point, their distribution is expected to shift and their numbers decline due to ongoing climate change. A 2017 report by Massachusetts Audubon predicted that by 2050 the black-capped chickadee population is likely to disappear from coastal areas of Massachusetts and decline substantially throughout southern New England as rising temperatures push their range to the north.

For now, if you want to attract chickadees to your backyard, provide feeders (they are one of the easiest birds to attract to a feeder), black-oil sunflower seeds and suet will do the trick, and some standing dead trees for cavity nesting sites (they also like nest boxes).

While chickadees are around all year, I think of them as winter birds. Watching them at my feeder as snow lightly falls is a wonderful way to welcome winter in New England.

Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com. Read more of her Nature News columns online.

Red Crossbills in New England

published Dec 17 2019 The Portsmouth Herald/seacoastmedia.com

I have been watching the “winter” birds return to my feeder – juncos and titmice, downy and hairy woodpeckers, cardinals and nuthatches. A birding friend who lives in Colorado just posted some gorgeous photos of red crossbills in his hometown of Estes Park. He said he is seeing them everywhere. I have never seen a crossbill (a type of large finch) even though we have both red and white-winged crossbills in New England, particularly in the winter. The North American range of the red crossbills that my friend Scott Rashid, founder of the Colorado Avian Research and Rehabilitation Institute, photographed extends down into the mountainous spruce and pine forests of Central America, while the white-winged crossbill range is mostly in the boreal coniferous forests of the north.

Both of these crossbills could, I think, be mistaken for a house or purple finch by a birder of my caliber (poor). I wonder whether I have seen crossbills in my backyard, but assumed they were house finches? Crossbills are larger than house and purple finches and both the white-winged and the red crossbill are rosy red all over with dark wings whereas the house and purple finches are reddish mostly in front. I’m describing male coloration – the females of all these species are drab, with the finch females being brownish and the crossbill females being yellowish-green.

Crossbills have a really wonderful adaptation to their lives in coniferous forests. Their bills cross at the tip so that when their bill is closed the tip of the bottom bill protrudes up and the tip of the top bill protrudes down forcing the upper and lower parts to cross each other. According to the Cornell Laboratory of Ornithology, crossbills employ a special technique using these unique bills to get to their favorite food, pine seeds. “A bird’s biting muscles are stronger than the muscles used to open the bill, so the Red Crossbill places the tips of its slightly open bill under a cone scale and bites down. The crossed tips of the bill push the scale up, exposing the seed inside.” They then extract the seed using their tongue and bill together.

One fascinating fact about red crossbills that Scott shared with me was the wide variety in overall size and particularly in bill size among what is now considered the one species of red crossbill (Loxia curvirostra). For example, there are types of red crossbills that are smaller in size with smaller bills who specialize in the smaller pine cones of hemlock trees while larger billed types will specialize in larger pine cones. There are currently 11 different types of red crossbill recognized in North America.

Another cool fact about both red and white-winged crossbills is that they are opportunistic breeders. Because their diet is largely composed of pine seeds (white-winged crossbills can eat up to 3,000 conifer seeds in one day!), because they feed pine seeds to their young, and because pine trees produce cones at different times of the year, these birds can breed whenever the seed crop is largest. This might mean nesting in the depths of winter – something I wouldn’t expect to see, a nest with young or some fledglings hanging out on a snowy afternoon.

The best time to find crossbills around is in the winter as they wander about in search of food. According to the Cornell Lab, “Crossbills are nomadic, especially in winter, and in some years irrupt far south of their normal range. At these times, they may show up in evergreen forests, planted evergreens, or at bird feeders.” Sometimes cone crops will fail in their breeding ground and migrants will show up further south in search of food. Making sure to include a variety of native conifers in your backyard can help attract them. Cemeteries and parks with ornamental spruce and pine plantings are also a good place to look as they often attract crossbills in winter.

Everyone I know who is a “real” birder has seen crossbills in New England in winter, so my personal challenge is to try to join the ranks. To that end I’ll be paying a little more attention to anything that looks like a house finch and to any reddish-pinkish birds hanging out in my conifers and feeding from the pine cones dangling from the upper branches.

Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com. Read more of her Nature News columns online.