April’s second spring moon was almost full as she rose through the cracks of the cottonwoods. The acequias were filling across/down the field and a small amount of rain had fallen two days earlier. Diminutive lime green leaves feathered the trees. I was just walking in the house when I heard the call.
 
I stopped dead in my tracks, stunned. Then wondered if I was having some kind of audio – hallucination. A paracusia, or audio hallucination is a form of hallucination that involves perceiving sounds without auditory stimulus.
 
After all, it had three years since I had heard one of the most beloved sounds that I associate with spring…I kept listening, sat down on the steps, my ears on fire. The unmistakable trill.
 
After a timeless pause, the practical side of me took over. I entered the house, got my recorder, and began recording the song.
 
I have been listening to the musical trill of tree frogs since I was a child, and I knew this song by heart. A gray tree frog was singing just beyond what I call the magic portal, a natural cathedral framed by bowed cottonwoods that opens into the next field.
 
After about an hour of listening and recording even the skeptic in me was forced to accept that this really was a gray tree frog. Sadly, I never heard a female’s answering call. It was also clear that this male frog was not being challenged by other tree frogs (who call out to establish territories as well as to attract females) because there apparently were no others in the area.
 
This latter fact did not surprise me. All frogs have been endangered since the 1960’s and many have become extinct.
 
“In Silent Spring” written in 1962 a brilliant and dedicated biologist, and true “mother of the environmental movement” warned us about the Great Silence that was about to descend upon us as a result of indiscriminate pesticide use, and no one listened.
 
Frogs and toads are the canaries of water, land and air. Because they breathe through their skin they are indicators of the massive amounts of pollution we are allowing to consume our planet “forgetting,” of course, that eventually these pollutants will kill humans too (the ultimate dis-connect).
 
Just before I went to bed that night I opened the door and heard the solitary tree frog crying out to the moon.
 
The next morning I compared my recording with the songs of grey tree frogs online, and of course they were identical.
 
For two days I researched every New Mexican tree frog and listened to about 50 recordings and came up with nothing that sounded like the recording I had.
 
How could this be? Grey tree frogs are denizens of the wetlands and forested areas of the northeast – east of the Rockies.
 
Meanwhile, my beloved gray tree frog is still singing his heart out even during the day, something I have never heard any of the Maine gray tree frogs do unless rain or heavy mist blanketed the mountains. At these times they sing periodically.
 
As of this writing, even in the wind my little friend is still calling – the voice of yearning crying out in the wilderness… Three days in a row.
 
At present I have no answer to this particular mystery and welcome any commentary the reader might have.
 
What follows is a little natural history on these one to two inch frogs that come in every shade of gray to green, depending upon the vegetation they inhabit.
 
The gray tree frog's scientific name is Hyla versicolor. The frog’s ability to alter its skin color also changes with respect to the time of day and the surrounding temperature. When my brother and I were children we would capture these frogs and place them on leaves, lily pads, wild grasses, bark, lichen etc. just to watch how fast they could change color! Their skin becomes much lighter at night and darker during the day.
​
Gray tree frogs hibernate in the winter by taking refuge in trees. They survive sub -zero temperatures by producing glycerol to "freeze" during which time they also stop breathing while still being able to maintain interior metabolic processes. A virtual miracle, that.

Supposedly the gray tree frog's range covers much of the eastern United States, from northern Florida to central Texas and north to parts of southeastern Canada but obviously, some of these frogs are moving west, or were here in the first place. Tree frogs are an arboreal species that occupies a variety of wooded habitats. They are most often found in forests, swamps, on agricultural lands and in wooded backyards.

All need access to trees and a water source. I don’t know when it occurred to me that I am surrounded by the perfect habitat here as well as in Maine. When gray tree frogs are young and newly metamorphosed, they usually remain near the forest floor tucked into bark, detritus, or high grasses; later they transition to the forest canopy. As an adult I have captured some that like to hide in the rough bark of the white pines next to my brook (Maine).

Adult gray tree frogs mainly prey upon different types of insects at night because they are nocturnal. Mites, spiders, plant lice, snails and slugs are common prey. They may also occasionally eat smaller frogs, including other tree frogs. They search for insects in trees, where they can climb vertically or move horizontally with their fantastic  toe pads that cling like suction cups.
The males begin trilling in early spring, shortly after emerging from hibernation. In the mid-range areas males begin calling in late April to early May. In Maine I don’t begin to hear them until late May. Males call to females from trees and bushes that are usually close to overhanging streams or standing water.

The exact timing of breeding for gray tree frogs varies based on temperature and their location throughout the range. Most reproduction takes place early on, although the musical trilling lasts from late April to early August (May through September in Maine). Individuals may mate up to three times in a season.

Males are very territorial and will fight other males to defend their area. Fights may last 30 to 90 seconds and consist of wrestling, shoving, kicking and head butting until the subordinate male retreats. Females are sexually di-morphic (bigger) and initiate mating by approaching a calling male.1,000 to 2,000 eggs which are externally fertilized by the male. Since actual mating occurs while the frogs are floating in water, eggs are deposited into the water in small clusters, attached to a reed or some kind of floating debris. Tadpoles usually hatch after three to seven days, depending on the water temperature. As youngsters, these frogs are painted scarlet or orange-vermilion with black blotches around the edge of the crests, so unlike other species they are easy to identify. Bodies and tails are patterned with many specks of black and gold. Like most tadpoles, they eat algae and organic detritus found in the water. Tadpole development depends on water temperature and is variable, but vernal pools must have standing water for some time, a real challenge here in Abiquiu.

After three days of trilling this poor little frog must be exhausted. I can only hope that there is one female that will hear his call… 

Every time I think the Evening Grosbeaks are thinning out or even migrating en mass, they return. I have had a huge flock of these golden birds on my porch all winter and spring. Every morning the air is flooded with raucous finch bird song.

According to many sources these beautiful birds are nomadic in southern areas but their presence here has been consistent. Irruptions (or rapid increases) of these birds in fall and winter are a common response to changing food supplies. Perhaps they stay around here because I feed them (as so many people do), but even with a stable food supply they will leave eventually. Western populations migrate to higher altitudes to breed sometime this spring and then return to the lowlands during the winter.   

In the Northeast, where I come from, the summer arrival of the grosbeaks is an event not to be missed because they migrate north to breed and are gone again within three months. In the last few years the bountiful flocks have been absent, having been replaced by a few breeding pairs. No one knows why Grosbeak numbers are in decline but apparently this downward trend holds for much of the US. While the pattern of decline is clear, the potential causes are murky unless one factors in the usual, Climate Change and insecticide use. I do know that these finches have adapted to having a regular supply of sunflower seed by growing a larger beak.

Evening Grosbeaks interest me because they are an example of a bird that migrates in a limited way, (altitudinal) and one who also makes a long distance seasonal flight.

 Migration is the patterned movement from one place to another that occurs in birds, mammals, fish, reptiles, amphibians, insects and crustaceans. Migration may also occur at the cellular level.

Migration can occur seasonally or just once in a lifetime.  Birds like grosbeaks migrate to find food and to reproduce, but I can’t find any data on why these birds move from Abiquiu to higher altitudes to breed when there are extensive cottonwood canopies  around here and a regular food supply, so there must be other unknown factors.

It’s important to distinguish between birds that migrate seasonally for food and reproduction from those who are forced to leave one place for another because of human induced habitat loss, and Climate Change. Is it possible that one of the reasons the grosbeaks move to the mountainous ranges is to escape the heat?   

Like scientists, I have been intrigued by migration because we know so little about how birds and animals know what they know, and because, unfortunately, whatever capabilities animals have developed over millennia are also being interrupted  in ways that we can barely comprehend.   
​
Multitudes of studies indicate that 1,800 of the 10,000 remaining bird migrating species probably use a wide variety of mechanisms to navigate, including the stars, the sun, olfactory (chemical) cues, internal circadian rhythms that change in response to the seasons, and Earth's magnetic field. Controversial field theory may also offer an explanation. But the point is, we don’t really know. The mysteries of bird migration continue to haunt me with questions I can’t answer.

Here are a few examples of the ways bird migration has changed over the years:
1. Evening grosbeak migration patterns are shifting.
2.  Some Canadian geese migrate seasonally; others remain in some states year-round.
3. Lesser black-backed gulls began appearing regularly in the New Jersey area in the 1970s, and  are now fairly common winter visitors.
4. Sandhill cranes that used to migrate to Florida for the winter have stable winter populations in the state of Tennessee, and this year we had whole flocks of these birds who spent the winter here rather than moving further south.
5. Not all Rufous hummingbirds migrate to the tropics for the winter. Some are now flying south to areas like Alabama and Florida to remain there for the winter.
6. Barn swallows habitually migrated to South America during the winter but at present they also nest there in addition to moving north to breed.

We may not know how migration works, but we do know the patterns of migration are changing and that Climate Change is a reality. My fervent hope is that somehow most species, who are all our “elders” – humans, after all have only been around for 200,000 years - (plants for 450 million years, animals for 350 million years) - may possess strategies that we can’t even imagine to survive the damage that we have brought upon all living things, including ourselves.