Spring is in the air…. Uh, I mean water!

It was the sound that first attracted my attention. Initially, I thought that it sounded like a flock of birds, but as I approached a pond, I realized that was not the case. The almost chirruping sound didn’t fit with any frogs I had heard before. As I scanned the scene before, my roving vision finally alit on a small section of brownish water dappled with green algae and stalks of dead reeds – there were moving bumps there. When I came closer, I finally realized that it was a mass of writhing and continually moving toads, engaged in what resembled a bit of a battle. It was actually what could be called a mating contest. (Click on a photo to see it larger; then arrow back to return to blog.)

The sound made by the male Eastern American toad (Anaxyrus americanus americanus) when he is ready to breed has been likened to an old-fashioned ringing telephone. It can last from 6 to 30 seconds and when multiple toads are calling at the same time, they create a very loud and penetrating “concert”. It doesn’t sound like a phone to me; you can judge by listening to the video.

I only saw a couple of the toads with inflated throat sacs. The sound was very loud, however, and the water was roiling with moving heads topped by periscope eyes, warty bodies and thrashing legs.

Before examining how the toads were going about their reproductive endeavor, a little biology lesson. Toads are a sub-group of frogs; while most frogs have moist skin, toads generally have drier and wartier skins. They vary greatly in color, including shades of yellow, brown, black and red, and may be speckled or have solid hues. The skin color can also change in response to stress, temperature, humidity and habitat.

 

American toads have two glands at the top of their head behind the eye crest. These are parotid glands that produce a neurotoxin, bufotoxin, which can sicken and even kill a predator. The milky substance can produce skin irritation in human beings and can be dangerous to smaller mammals (like dogs).

 

 

Like birds, toads have nictitating membranes, transparent eyelids that help protect the eye. They sometimes raise the nictitating membrane half-way so that they retain sharper vision.

 

 

Toads actually spend a lot of their lives on dry land, eating insects as well as worms, slugs and other small invertebrates. A particularly fascinating fact is that they use their eyeballs to help swallow food – when they ingest their prey, the eyeballs sink down into their mouth and help push the food down their throats!!!

At times, they created little whirlpools as they bumped up against one another or tried to mount a neighbor.

 

 

Sometimes, a large female with a smaller male atop her would rest quietly under water, apparently trying to avoid notice. This strategy did not always work, however, and sometimes one or more other males would try to join the pair already in amplexus (i.e., when the male grasps the female with his front legs and fertilizes the eggs as she releases them from her body)..

The female toad ejects her eggs in two strings, which are immediately fertilized by a nearby male spurting out a stream of sperm. (Frogs lay their eggs in clusters.) Tadpoles will emerge from the eggs within 2–14 days and reach adulthood within 50–65 days. They become sexually mature at 2-3 years.

In one case, I developed a real sympathy for a particularly large female. She had a small male astride her who resembled her in coloring and they looked to be peacefully joined. Then another male spotted them and he launched a sneak attack, trying to usurp the position of her already-present suitor. The first male clung on tightly.

No. 1 pushed No. 2 away with a hind leg again and again.

In the meantime, a great blue heron (Ardea herodius) who had been feeding on the other side of the pond, made its way over to the site of toad frenzy. S/he had been eating small fish and amphibians.

I thought the heron would plunge into the midst of the numerous toads for an easy meal, but instead the bird looked around and then skirted the group, veering away to the shoreline. Perhaps some instinct made the heron avoid the group during a reproductive event? Or s/he was put off by the vigorous activity of the potential prey?

A second rival toad then joined the first, who was still trying to get the original mating male out of the way. Eventually, a third, fourth and yet another male joined the group and the poor female was weighted down by 5 – FIVE! – male toads all vying for the prime spot on her back. Often her head was pushed down under water.

The first male clung on with great determination, often being pushed down under water as well as the other males piled on. He was NOT going to give up.

Ms Toad did not like this state of affairs. She laboriously began moving from a deeper spot in the pond to the pond’s edge. This was a slow process, made difficult by the clinging crowd who must have weighed a good deal as a group.

I thought she might be trying to get to more shallow water so the toad “knot” would not keep her submerged. Toads can breathe under water like frogs because they can absorb oxygen through their skin. They do have lungs, however, and if these fill with water, they can drown. A fellow Facebook nature lover told me that she had seen expired female toads with males still clinging to them. A toad knot can therefore unfortunately result in maternal mortality – the demise of a mother giving birth (to several thousand eggs; most of the tadpoles do not survive).

I soon left the scene after Ms Toad had reached the side of the pond and could keep her head above water. It was noticeable that her throat pouch was inflating and deflating – perhaps she was breathing deeply to compensate for lack of oxygen when she had to suffer a submerged head due to the over-amorous males.

 

Inhale!                                                                  Exhale!

I know I am anthropomorphizing, but I do believe that she likely felt the amphibian equivalent of relief and was looking forward to the end of that day!

When those loving instincts leave you dangling

This was not a planned blog, but I recently observed something that simultaneously intrigued, amazed and astounded me, so I wanted to share it with those of you who may not have witnessed this either.

Like many gardens in my neighborhood, my yard has its fair share of leopard slugs (Limax maximus), but they don’t bother me as they do some other people who complain about them eating their vegetables. Until recently, I never thought about the slugs much and certainly didn’t wonder about their life cycle. Then my friend Mary posted a lovely photo of two intertwined leopard slugs mating and my interest and curiosity were piqued.

A few days later, a fellow nature lover, Ace, reported that he had a cool photo to show me – and there on his iPhone was a photo of mating leopard slugs. It turns out that their anatomy makes for a somewhat bizarre spectacle – at least to a human being if not a fellow slug. Now I really wanted to see this phenomenon, too, and I followed Ace’s recommendation, going out into my yard at night with a flashlight to see if I could find some amorous mollusks. Lo and behold – as I rounded the corner of my house, there were three pairs of large slugs getting ready to reproduce! They were leaving glistening slime trails on the brick wall as they slowly got into position.

The slime that the slugs exude has multiple purposes – they can leave a trail behind them as a signpost to the way home, they can numb the mouth of a potential predator with the mucus as a means of defense, and they can broadcast their interest in some reproductive behavior by emitting pheromones to attract a potential mate.

They don’t actually need to mate to reproduce – each slug is a hermaphrodite and can fertilize its own eggs with no need of outside assistance. Slugs have an organ called a spermoviduct (SO), which has two parts – one for the sperm (vas deferens, VD) and one for the ova (oviduct, OV), as seen as this drawing from the Wikipedia page.

Some slugs apparently like reproductive acrobatics, however, and seek out a partner. The mating begins with a pair of slugs following one another around and nudging and licking one another. (A couple photos look browner – I took those with a flash but most were taken with one hand holding a small camera and the other shining a flashlight near the slugs.)

 

They then begin to curl up together and suspend themselves from a long mucus rope, which is somewhat stronger than the slime that they usually exude. They form a kind of writhing ball as they intertwine their elongated bodies (see this video for an example).

Next comes the awesomely weird part – out of a gonopore on the right side of their heads (the elongated tentacles are for vision) come their translucent mating organs (penises)! This video, which is shown in a horizontal position, lets you see how this happens.

Wouldn’t this interesting anatomy and reproductive behavior make an interesting plotline for an SF novel about a genderless society?

 

      

Because the slugs are hanging upside down, gravity helps pull down their reproductive organs, which are pumped full of body fluids until they are as long as the slugs’ entire bodies! Their penises are everted (turned inside out) and the two mollusks intertwine these just like their bodies. They take a while to exchange spermatophores as the penises twirl, intertwine, elongate and pull back to look a bit like a chandelier.

  

When the creatures have been joined at the neck for some time, they begin to slowly withdraw their reproductive organs, which are now carrying genes from another parent.

              

After they separate, one of the pair usually consumes the mucus rope from which they dangled in love as it carries extra nutrients which they can use after their vigorous efforts.

          

 

 

Each slug may spend some time examining its gonopore (above) – and perhaps they are helping push back in the penis when they do this, too. After watching the process for two pairs of slugs, I decided to give the third pair some privacy during their mating tryst. On the wall beneath my screened porch, I discovered another slug with a mucus rope dangling from its tail – leaving me with a little mystery as to why this might have happened. A partner slug was not in evidence except for a much smaller slug – perhaps the big one tried to mate but the younger one was not ready. These mollusks with a life span of 2.5-3 years don’t become sexually mature until they are 2 years old.

    

I do know that at least three and perhaps six slugs will each be laying up to 200 eggs somewhere in the yard. And when I see them in the future, I will undoubtedly always be picturing them in my head doing their dangling dance with intertwined translucent blue tubes that will help promote their future generations. My discovery of their life cycle has also reinforced my support for scientist Hope Jahren’s (Lab Girl) observation: “…being able to derive happiness from discovery is a recipe for a beautiful life.”

Avian generations in the making – part 3B: fledgling and post-fledgling care

The number of days after hatching when young altricial birds leave the nest is fairly predictable for many species; knowing those approximate dates is helpful if you want to plan a day to watch fledging happen. I can often arrange to sit and watch a nest box on the appointed day for several hours.This has enabled me to see several broods of Eastern bluebirds and brown-headed nuthatches make their leaps to freedom on the path to adulthood.

When it is time for fledging, parent birds encourage their babies to leave the nest. They may entice them by perching nearby with some food but not bringing it to them. Or they fly to the box with food and then go to a branch instead of feeding. The Eastern bluebirds (Sialia sialis) in my yard will hover in front of the nest box like a hummingbird, sometimes with food in their mouths; perhaps they are showing the young ones that flight involves flapping wings.

While in some species, parents appreciate help from older children in caring for a current brood, Eastern bluebirds apparently do not. This may be because they see the previously fledged young as competitors for food. In my yard, father bluebird especially was chasing the young of earlier nests away from the feeders, not only when they begged but also when they fed themselves.

 

When fledging day arrived for the bluebirds’ third brood, one of the older siblings (I’m not sure if it was a female or male) was very interested in seeing the third brood fledge. He imitated his parents, hovering in front of the nest box so the young ones could see him.

 

Again, however, the parent bluebirds chased him away.

This did not deter the immature bird, however. He waited for the parents to go get food and again took on encouraging the young siblings. It was fascinating to watch!

 

The parents returned and drove him off with a show of bad temper.

Eventually, the babies did fly out of the nest box into a nearby crepe myrtle. There, they continued to call for food with a wide-open mouth.

    

This gaping behavior stimulates the parents to feed their offspring and the offspring can be very insistent and persistent in begging for food.

    

Eastern starling (Sturnus vulgaris)

     

Carolina wrens (Thryothorus ludovicianus)

  

Common grackle (Quiscalus quiscula)     Royal tern   (Thalasseus maximus)

This behavior can go on for days, especially when the young ones cannot yet fly, like this recently fledged Northern mockingbird (Mimus polyglottos).

 

 

The birds that feed their young ones on the ground, like the American robins (Turdus migratorius) have it a bit easier than those that feed juveniles perched on wires, like these barn swallows (Hirundo rustica).

   

I can imagine that the mother and father get to a point of thinking, “Enough already!” as those large fledglings continue to beg for food; this parent Northern cardinal (Cardinalis cardinalis) did not seem willing to go out for yet another bug for the young one.

But some young birds can be very insistent, even when it is obvious that they are now fully capable of finding some food on their own. This parent chipping sparrow (Spizella passerina) seemed willing to be a feeder for a while longer.

                        

The parent-child feeding routine that often catches people’s eye is when a young brown-headed cowbird is being fed by a (non-voluntary) adoptive parent. For example, here we see a male hooded warbler (Setophaga citrina) bringing food to a brown-headed cowbird baby (Molothrus ater) after the youngster spent quite a while loudly crying out for a meal and hopping around on branches after the parent to convince him that he needed to be fed.

  

Of course, at a certain point the parents do stop feeding and the young set off on their own. They may check out nearby nest boxes, either scouting homes for next season or looking for roosting boxes for the cold winter nights, like these Eastern bluebirds. They may groom a bit to remove the last bits of fluffy feathers, like this red-shouldered hawk (Buteo lineatus). And then they are ready to spend an autumn and winter getting ready to repeat the cycle, this time as the parent birds. And we can look forward to watching the process again. 😊

 

        

Avian generations in the making – part 3A: raising and feeding babies

So here in North America, it’s approaching winter and it may seem a bit weird to have another blog at this time on birds raising their young. But I wanted to complete the series even though it has been delayed because of my volunteer activities and commitments the past month. Also, it is now late spring in the Southern hemisphere so for some people this is seasonal and there are other birds around them that are getting ready for babies, though different species than these American robins (Turdus migratorius). Because this part kept growing longer as I worked on it, I’ve divided it into two parts – this one on raising the babies until fledging and the next one on fledging and post-fledgling care. I hope all of you who read this will enjoy it no matter where you live.

It’s fascinating to me to watch the birds during their reproductive cycle; I always learn something new. Once parent birds have completed a nest to their liking, the female lays her eggs and proceeds to brood them, with some species sitting on the eggs almost full time right away and others taking breaks.

           

Carolina wren (Thryothorus ludovicianus)              Eastern bluebird (Sialia sialis)

An acquaintance recently told me about a friend of hers who commented that she had seen a very pregnant goose that was so fat, she was waddling. The acquaintance proceeded to give an avian reproduction lesson to her friend – a woman in her 80s – who apparently did not know all birds lay eggs! Even after babies hatch, the Canada goose (Branta canadensis) may still look well-fed!

Some bird species have young who are “precocial”, that is, they are covered with downy feathers and have open eyes when they hatch and are soon able to feed themselves. These species include turkeys and ducks, like these mallards (Anas platyrhynchos), and the young often leave the nest soon after birth (which makes them “nidifugous” – good Scrabble word!). The newborns may look fuzzy but it’s not long before they start to take after their parents’ looks.

Other birds, such as songbirds, are altricial (as are human beings) – they are naked and helpless at birth and require considerable care before they can walk, fly and feed themselves. If you have some in a nest that is easily observable (and you can take photos when parents are not there so you don’t distress them), it’s interesting to see how the babies develop.

               

Carolina chickadees (Poecile carolinensis) on 18 and 22 April           

Brown-headed nuthatches (Sitta pusilla) on 13, 25 and 29 April

 

 

Eastern bluebirds (below)

     

As the mother incubates the eggs, her mate will often feed her so she doesn’t have to leave the nest. This young osprey (Pandion haliaetus) was assiduous in bringing his female life companion fish. Then as the babies hatch, in many species both the male and female parents get busy bringing the young frequent meals.  It’s estimated that Carolina chickadees, for example, will bring over 5000 insects to their brood before fledging!

Northern mockingbird (Mimus polyglottos)

     

House finch (Haemorhous mexicanus)  and Red-headed woodpecker                (Melanerpes erythrocephalus)

              

Orchard oriole (Icterus spurius)                  Blue grosbeak (Passerina caerulea

  

Eastern phoebe (Sayornis phoebe)

In some species, the previous year’s young will help their parents with the new brood. Brown-headed nuthatches and American crows are examples of this. A pair of Canada geese that I observed this past spring seemed to have a domestic goose helping them out.

The parents have other chores, too. They must keep the babies safe from predators – Both American crows (Corvus brachyrhynchos) and common grackles (Quiscalus quiscula) will be chased away by songbirds, for example, because these birds will raid nests to eat eggs and babies. But the grackles must also protect their own young against the crows, pursuing them non-stop to drive them away.

 

For other birds, protecting the young can be more difficult. This mother wood duck (Aix sponsa) was raising her brood in a pond that was home to at least three large snapping turtles (Chelydra serpentina). Ultimately, another birder and I thought she only had two ducklings survive.   

Keeping the nest reasonably clean is another chore. The babies make this task a little easier than you might think because they defecate into a mucous membrane that forms a sac. When you watch a nest box, especially when it gets closer to fledging time, you can periodically see the parents flying out of the box with a white blob in their mouth, which turns out to be a fecal sac. They either discard it elsewhere or sometimes eat it for some nutritional benefit.

        

Brown-headed nuthatches

This year, I was surprised to have caught a female blue grosbeak during the cleaning – it appeared that she was actually pulling the fecal sac from the baby! Later, I read that some species stimulate defecation by prodding the babies’ cloaca so they can get on with the chore. I also caught a photo in which a baby bluebird had just presented its rear end to the parent for removal of a sac. I could imagine that some human parents might think a fecal sac would be a cool avian adaptation for their babies to have – no more dirty diapers and expense for diapers either! (An idea for an SF short story?)

     

 

After all their efforts, the parents are usually ready for those babies to fledge – the subject of the upcoming last blog in the series.

 

 

* Not all the photos in this blog are of great quality, I know, but my intention was first to show behaviors and secondarily to have some nice shots in the blog.

 

 

Avian generations in the making – part 2B: nesting in nature

My last blog looked at birds’ nests in man-made structures and there are plenty of birds who take the opportunity to use such sites. Most birds, however, make their homes out in nature – in shrubs, trees and on the ground. This is a bit of a long blog but I want to share views of different species at work.

There are different types of nests; a few types that we see in North Carolina include:

  • Cavity nests – holes in trees, made by the parents themselves or adopted as a home when birds like the cavities made by others
  • Simple scrapes – these are shallow depressions scratched out on the ground and they may be lined with materials or left to look like the rest of the surrounding ground
  • Cup-shaped nests – these structures are like small bowls and may be lined with materials like those used in nest box nests. They can be made of varied materials – swallows use mud while American robins and other birds use plant materials.
  • Platform nests – these nests are usually quite large and comprise large twigs and small branches
  • Plate nests are a bit similar to platform nests but much smaller and less organized; they may consist simply of a few twigs arranged in a shallow bundle
  • Pendant nests hang from branches.

When birds look for a cavity site, they may seek out a new spot on a tree trunk or investigate already existing cavities. These Eastern bluebirds (Sialia sialis) at Sandy Creek Park were examining one particular hole with interest, but a downy woodpecker was interested as well so there was some rivalry. The female bluebird chose to just sit on a nearby branch while her mate looked at the hole numerous times trying to make a decision.

    

Red-headed woodpeckers (Melanerpes erythrocephalus) excavate larger cavities in tree trunks to raise their broods. They may visit various trees before deciding on a spot.

      

Pileated woodpeckers (Hylatomus pileatus) may use the same holes year after year. They make holes for resting as well as for nesting and often include a “back door” so they can make a quick escape if a snake shows up.

          

Brown-headed nuthatches (Sitta pusilla), like this one at Jordan Lake, can be very industrious in excavating their nest cavities. You can watch them pecking away at the wood of a tree trunk or branch, scattering wood shavings and removing bigger bits of softened wood in their beaks to achieve a hole of the right depth for their babies. (See a short video of one at work here.)

   

I also saw nuthatches making nests on the edges of a farm and near the NC Botanical Garden. The pair working on a nest at the Garden were doing this with a great horned owl on a branch overhead, as well as a red-tailed hawk and crows who were raising a racket. Their presence didn’t bother the little birds; these nuthatches also appeared to have help from a previous year’s youngster willing to help the parents raise the new siblings.

 

 

    

Carolina chickadees (Poecile carolinensis) also dig out small holes in trees and snags.

      

Killdeer (Charadrius vociferous) use scrape nests which may look exactly like the surrounding area; their eggs then blend in really well with the environment and can be difficult to see.

When I first saw this nest suspended from a tree near a bridge, I had no idea which bird had built it. A birding friend had fortunately seen the parent bird fly to the nest – it belonged to a Northern parula like the one shown below (Setophaga americana).

    

I was lucky to see a female orchard oriole (Icterus spurius) collecting nice soft lining materials for its nest this past spring.

         

A red-winged blackbird (Agelaius phoeniceus) was doing the same with cattails – an obviously appropriate source for bird bedding!

       

Mourning doves (Zenaida macroura) and Northern mockingbirds (Mimus polyglottos) make fairly shallow, twiggy nests (“plate nests”). It makes you wonder if eggs ever roll out of them through cracks in the loose, low walls.

   

Many birds make cup nests and spend a good amount of time collecting the materials to produce them. Here you see American robins (Turdus migratorius) gathering grasses – they tend to fill their mouths as much as possible before flying off to the nest-in-the making.

      

Red-eyed vireos (Vireo olivaceus) will also attempt to get several pieces of bark into their beaks before flying back to the home site. The photos here are dark as the bird was deep in shrubs where little light was penetrating.

        

Blue grosbeaks (Passerina caerulea) weave what looks like a cross between a pendant nest and a cup nest; they also add man-made materials such as rags, cellophane, newspaper and bits of plastic.

    

Great blue herons and ospreys are builders of platform nests.The great blue herons (Ardea herodias) carry large twigs and branches to furnish a nest. At Sandy Creek Park they have been using the same tree-top platforms for several years now.

     

Last year, I saw this osprey pair (Pandion haliaetus) build their first nest from scratch; they weren’t enthusiastic about me being in the vicinity and would perch or fly overhead to give me “the evil eye” – sometimes calling to one another to sound the alert that they had spotted me down below.

 

 

This year, they were busy refurbishing the nest – these birds with longer-term mates may use the same nest year after year. Again, they would stop their work to stare me down.

 

The Acadian flycatcher (Empidonax virescens) makes a cup nest that is well-hidden among the leaves of the tree spot it chooses. A friend saw the pair constructing this nest and it was done by the time I visited. It seemed quite a tight fit for mom to sit in while brooding her eggs.

The bird whom I enjoy seeing most during nest construction is the blue-gray gnatcatcher (Polioptila caerulea). These little birds are very active and often don’t sit still for long as they feed in shrubs and trees. When they are busy making a new home though, they take their time to do a good job. First, they locate good locations for the materials they use – leaves, spider web to hold the leaves together and pieces of lichen to cover the outside walls.

      

They affix the lichen carefully to make a really beautiful, compact and elegant little cup. The female then sits in it and moves her body to ensure it gets the right shape and dimensions for her upcoming brooding.

     

The male and female both work hard on the nests and this year I got to see three pairs at work. In two cases, it was lucky I saw them flying to and fro because their nests blended in really well with the tree.

Unlike the cavity and platform nesters, the cup and pendant nesters usually need to build a new nest each year. At the end of the summer, for example, the blue-gray gnatcatcher nest had already deteriorated considerably with the rain and wind, even though it was a fairly calm and dry season.

 

Once the nest is complete, the avian parents brood and feed their babies before fledging and this will be the third part of this series. For now, I leave you with the male and female ospreys as they watch the birdwatcher….