Great blue herons have a diverse diet, including rodents. AP Photo/Charlie Neibergall

My property borders a freshwater marsh so the sighting of great blue herons is an almost daily occurrence. This spring, however, I’ve been seeing them walking around my yard at times and appearing to be in a hunting mode. Last week, I happened to look out at just the right moment to see one heron stealthily walk behind a fence and then grab an unknowing chipmunk. Since there are many chipmunks on my property, I wondered if this is what might be attracting the herons onto the grounds. Are chipmunks a regular part of their diet? I wasn’t aware that herons catch prey that aren’t aquatic. Thank you for your insight about this.

– Jean Cucci, Edgecomb

Great blue herons have an amazingly diverse diet, especially throughout the year. Most have to migrate away from Maine in the winter because the food they’ll eat becomes either scarce or hard to find, but through the breeding season we see them go after all sorts of animals. In the northeast, fish are definitely the top item on the menu, but our herons aren’t picky and will catch what they can, especially with the least amount of effort.

Most of the calls we get at Maine Audubon from people who see herons hunting in fields come later in the summer or in the fall, times when there are more rodents available and when the heron may be done nesting and can wander farther from its nest in the wetlands. As a side note, most people assume they are seeing cranes because they don’t associate herons with being in fields, and while we do have sandhill cranes in Maine (in small numbers), both can be seen hunting in these habitats.

From fish to mammals, plus amphibians and even other birds, great blue herons are amazingly adaptable at finding something to eat. I’ll always remember a video sent to me a few years ago from a Scarborough resident who had a heron repeatedly stalking chipmunks from the deck; a great natural control for that “pest” problem. If there is one takeaway, I hope people realize the diverse diets of many of our animals and make sure they avoid using rodenticides if you have a problem around your home.

FROGS STRESSED OUT BY NOISE POLLUTION

Spring peepers are out in force. TNS

Here’s an interesting question I received from one of the editors at the Portland Press Herald, Peggy Grodinsky of Portland:

The peepers are going full bore at Capisic Pond. It’s a wonderful racket! But the pond is actually quite near the Portland Jetport. And when a plane flies overhead, the peepers stop, then they only gradually start up again. My partner wondered if I just couldn’t hear them over the noise of the plane, but I’m pretty sure that’s not it; I think they stop peeping. What does that mean for their health? It seems like it can’t be a good thing. And what other wildlife do those planes affect?

There are so many sounds – from cars to planes, and, as we roll through spring, you’ll probably also hear leaf blowers, which have become background noise that humans often tune out. Unfortunately, for a lot of our wildlife, these anthropogenic noises can cause lots of problems. This is especially true for species that rely on noises that they produce, be it vocal or mechanical, for mating, which is the exact problem for the peepers that Peggy is hearing at Capisic Pond.

Let’s start by thinking about the life cycle of some of our frogs. After overwintering as adults in some muddy spot (see my last column on turtles for more on reptiles in winter), they’ll move to a vernal pool during the first warm rains in the spring in an annual event known as a “Big Night.” What comes next can only be described as an amphibian orgy. You’ve probably heard them most nights since, trilling loudly in an attempt to attract a mate and breed, leaving behind a large egg mass. The “trilling loudly” part is crucial; similar to the birds singing in the spring, you could think of the loud noises of spring peepers or other frogs as their song to attract a mate.

Several studies have looked at how anthropogenic noise pollution has caused decreased production rates in frogs. It shouldn’t be much of a surprise since we know how noise can negatively affect humans, but this is definitely an issue for species that are dependent on transmitting and receiving acoustic signals. Displacement was commonly reported in areas with lots of noise pollution. The frogs would leave and try to find a new location where they could be heard. This is important to consider because with increased fragmentation of habitats, the reach of noise from adjacent roads or populated areas will extend into those areas much more than we realize.

There are also physiological changes being reported in frogs exposed to noise pollution, including lowered defense against disease (through “impaired production of antimicrobial peptides”) and increased stress levels, which caused a male’s color to change unfavorably, thus making him less successful in finding a mate.

Stressed-out frogs might not be the most charismatic of animals to help raise awareness, but as a species that is so dependent on the noises they make, they are a good canary in the coal mine to better our understanding of the impacts of noise pollution.

Do you have a nature question for Doug? Email questions to ask@maineaudubon.org and visit maineaudubon.org to learn more about virtual and backyard birding, online classes and other programs about wildlife and habitat.