The birdy breeding cycle 2020 – 3: raising young

This year, most of the birds that visit my yard chose to build their nests in places where I didn’t see them. Only the brown-headed nuthatches, house wrens and Eastern bluebirds chose to use nest boxes. The Carolina wrens (Thryothorus ludovicianus) began to use a nest box but their nest was invaded by ants before I had noticed so they abandoned that site. Still, I was able to watch parents with babies, both at home and out on the nature trails.

There are two major kinds of baby birds. The altricial birds hatch as helpless young who must develop their sight and feathers, requiring parental care until they can fly from the nest. They include the songbirds that you may see often, such as chickadees, nuthatches, cardinals and bluebirds, whose babies are seen below shortly after hatching and after several days of development.

 

In contrast, the precocial bird babies can quickly move about on their own after hatching and are able to begin foraging for food themselves as they follow their parents around. In some cases, the parents may also feed them. Examples of precocial birds include killdeer, ducks and Canada geese (Branta canadensis) as seen below.

The nest I watched most closely this season was built by brown-headed nuthatches (Sitta pusilla) in a nest box. Carolina chickadees were also interested in that spot, but the nuthatches won out. Mama Nuthatch laid six eggs, four of which hatched. She and Papa were very hard workers, flying to and from the box countless times per hour. Like other seed-eating birds, they fed their nestlings insects because the babies need lots of protein for their development.

 

They were devoted parents, flying to and fro with food, carrying away fecal sacs and chasing off other birds who used the nest box as a perch. All their care was no match, however, for a pair of birds who are known to be quite aggressive during nesting season.

 

I first learned of house wrens’ (Troglodytes aedon) intolerance of other nesting birds in their vicinity when they invaded the nest of a banded female Carolina chickadee (Poecile carolinensis), whom I had named Chantal. Her babies were hatching and the wrens went into the nest during her absence and killed them. That experience made me hope they would not return to my yard the next spring, but they seem to like the area. This year they visited all the nest boxes in my yard and the male began nests in several of them to keep away other birds. It is thought they may drive away other nesters in order to reduce competition for food when it comes time to raise their own young.

 

The wrens finally settled on a nest box and I thought they would leave the nuthatches alone. Their young ones got to the brink of fledging and the parents were encouraging them to fly out. Sometimes, they would fly up to the box as a youngster peered out into the big wide world and just hover with the food in their mouth.

 

 

They would perch atop the box and call. Eventually two took the leap (which I didn’t see); I thought the others would follow the next day. The parents were busy in the morning and suddenly all activity ceased. I guessed that the other two had taken flight, so in the afternoon I took a peak in the box. To my utter dismay, I found the remaining two nestlings deceased; the wrens had pecked them to death. ☹ I buried them in my flower garden with a small Buddha statue marking the site.

 

 

The nuthatches continued taking care of their fledged babies. They would follow the parents to the feeder poles, crouch down and flutter their wings rapidly as they begged for a morsel.

 

Eventually, the parents found a nearby branch in a large willow oak where they would crack nuts and feed their offspring. As you can see, the spot got a lot of use and could be easily identified by the shredded bark. The whole family still goes up there to eat their nuts from the feeders!

Many adult birds appreciate bird feeders as “fast-food” stops for themselves while they spend most of their time searching for meals for their nestlings. Even the species who mainly eat seeds feed their babies insects because the young ones need lots of protein as they develop toward maturity. The Eastern bluebirds (Sialia sialis) in my yard and other areas seem to favor caterpillars as a food of choice for their developing youngsters.

 

 

 

The pileated woodpecker parents (Dryocopus pileatus) take turns sitting on eggs and bringing food for their young ones.

The larger raptors bring in heftier meals for their offspring. This red-shouldered hawk grew up alone; those of us watching the nest didn’t know whether only one egg hatched or something happened to a sibling. The parents would bring small mammals for the baby to eat.

 

A pair of great horned owl babies (Buteo lineatus), located by Mary, a locally well-known bird photographer, appeared to be growing well the couple times I went to see them. I never saw the parents bring them food but assume they were well fed as they were venturing out of the nest the last time I saw them (a process called “branching”).

 

It seems that a young bird’s open mouth is a trigger for parents that they can barely resist. Until they mature, the fledglings have a pale white or yellow area, or in the case of American crows (Corvus brachyrhynchos) reddish, where their beaks join. This becomes very visible when they open their mouths wide to beg for food and parent birds have a hard time resisting the urge to stuff food down their throats.

The Eastern phoebes (Sayornis phoebe) at a local park were following their parents around asking for food.

They exhibited both the crouched wing fluttering and wide-open mouths as cues that they wanted to be fed.

  

The downy woodpecker (Picoides pubescens) juveniles did not seem to beg as much as the other birds in my yard. They just perched close to feeders or their parents and eventually mom or dad gave them a bit of suet.

 

The European starling young (Sturnus vulgaris) are especially demanding to judge by their behavior at my feeders. These are larger birds and the offspring are as large as their parents,

They are capable of feeding themselves but spend a good deal of time with wide open beaks demanding to be fed.

 

 

 

The starling parents usually give in, but you can almost think they look exasperated.

At least the immature starlings can demonstrate well how a bird looks with a full crop (i.e., the enlarged part of the esophagus that forms a muscular pouch in which food can be stored).

In between all the feeding, the parents have one other important nest duty – keeping the nest as clean as possible. They do this by removing fecal sacs, as this prothonotary warbler (Protonotaria citrea) was doing last year.

 

Some adult birds will actually eat the fecal sac. This is because the nestlings do not completely digest their food and the sacs therefore still contain valuable nutrients that the parents can use. I can imagine the parents are glad to be done with this duty once their young have fledged, however.

When you’re out walking or watching bird feeders, it can be entertaining to observe the birds as they nest and raise their demanding children. And it’s good to know that you may even see adult birds begin to drive away their babies, either because they’re tired of feeding them or because they are busy with a second or even third brood for the season.

The birdy breeding cycle 2020 – 2: nest-building

After courtship has taken place, the various bird species get down to the work of constructing nests for their upcoming broods. Even now in July, gray catbirds (Dumetella carolinensis) have been gathering up nesting materials, as have house finches (Haemorhous mexicanus) who have been followed around lately by the members of their first brood.

gray catbird P6147926© Maria de Bruyn res

house finch P7081079© Maria de Bruyn resThe sites they choose can vary considerably. Canada geese (Branta canadensis) tend to locate their nests at the edge of ponds if possible. In one case, a pair built their nest atop a beaver lodge.

Canada goose P4269282© Maria de Bruyn res

Canada goose P4070275 © Maria de Bruyn res

Ospreys (Pandion haliaetus) like to place their nests atop tree snags and will also use special platforms constructed by people for them. A radio tower or stadium lights, such as those at the right, will also do nicely, however.

osprey P5044393 © Maria de Bruyn res              osprey P6126775© Maria de Bruyn res

Northern cardinals (Cardinalis cardinalis) often choose shrubs and bushes; this one built her nest in a Japanese honeysuckle vine that I allowed to grow along the top of a fence surrounding my berry garden.

Northern cardinal 2G0A0652 © Maria de Bruyn res

Northern cardinal 2G0A0001© Maria de Bruyn res

Killdeer (Charadrius vociferous) seem to take the least effort in securing a spot for their nest. It is not uncommon at all to find them scratching out a very shallow depression in a parking lot, pathway or bare bit of ground. This killdeer put her nest on a patch of ground at the edge of a parking lot and, admittedly, it was not very obvious (Look carefully at the center of the photo).

killdeer eggs IMG_2885© Maria de Bruyn res

Nevertheless, people were walking across this patch of ground with their kayaks and canoes that they had just unloaded and the eggs were in danger, even if the parents did their broken wing display to try and lead people away from the area.

killdeer 2G0A8192© Maria de Bruyn res

I found a couple traffic cones and marked off the area, warning someone who had just parked nearby. Then I contacted the park rangers to tell them about it.

killdeer cones IMG_2887© Maria de Bruyn res

Fortunately, the rangers added a third cone and some tape to effectively cordon off the area.

killdeer IMG_5577 © Maria de Bruyn res

Carolina wren eggs IMG_1173© Maria de Bruyn resThe prize for weirdest nest sites will, in my humble opinion, always go to the Carolina wrens (Thryothorus ludovicianus). People in birding groups often post messages about these birds having built a nest under the hood of a car, in an old boot left outside, inside a little-used mailbox or on a door wreath or plant pot. I have a full-sized spare tire atop a tool cabinet and last year, the wrens laid eggs there.

This year, on one of my walks, I discovered wrens who were feeding their babies in a very awkwardly placed nest inside an old cable or wire box on a neighborhood light pole.

Carolina wren P5086279© Maria de Bruyn res     Carolina wren P5181735© Maria de Bruyn res

When I visited some time later, the nest was empty so the babies must have been able to fledge.

Carolina wren P5181745© Maria de Bruyn res

Many birds will use both tree cavities and nest boxes, depending on what is most convenient or available. Sometimes, they make their own new nest holes in snags, like this red-headed woodpecker (Melanerpes erythrocephalus).

red-headed woodpecker 2G0A0033© Maria de Bruyn res    red-headed woodpecker 2G0A0248© Maria de Bruyn res

Northern flicker P4217370© Maria de Bruyn res

This Northern flicker (Colaptes auratus) was very busy working on a new cavity as well. I followed her and her mate for some time but was never able to see them feeding nestlings as our area had several weeks of hard rain and the nearby lake flooded. I didn’t feel like wading through the lake to get to the snag to check up on them, even after the water had receded a bit.

Brown-headed nuthatches (Sitta pusilla) chose a snag that was usually in the water at the edge of Jordan Lake. The hole faced out into the lake so the fledglings were going to have to fly out and veer left or right immediately in order to get to a resting place!

brown-headed nuthatch P4175229 © Maria de Bruyn res

Eastern bluebirds (Sialia sialis) will use nest holes built by themselves or other birds in previous years.

Eastern bluebird P4070231© Maria de Bruyn res

Eastern bluebird P7070899© Maria de Bruyn resThis year, the Eastern bluebird pair who frequent my yard chose not to use their usually preferred nest box. I believe it’s because they could see me watching them and they don’t like that at all! If they see me with my camera, it doesn’t stop them from flying up to the feeder or sitting on a branch near the porch. If I point the camera toward the nest box, however, they stare at me in dismay, remain on branches near the box, and refuse to go in until I shift the camera away. They did come to my feeders multiple times daily to feed their first brood (one of whom is pictured at right), once they had fledged from a nest in someone else’s yard.

Eastern bluebird P7091193 © Maria de Bruyn resTo my surprise, a couple weeks back, the bluebirds chose to use a decorative nest box that I had bought for decoration. It hangs from a pole and sways in the wind and was not really sturdy. The roof began to let loose in the middle and the décor was curling up from the exposure to rain. But when I finally looked in the box when the parents were gone, I found four nestlings inside. They were pretty well grown already and I thought they might be fledging this past week. I didn’t see it, although I did watch a bit. Yesterday, I found one half of the roof on the ground and the nest was empty. I hope that the babies fledged and not that some larger bird plucked them out after the roof came off.

The materials used for nests can differ quite a lot. House wrens (Troglodytes aedon) make loose frameworks of twigs and the nests look pretty messy inside a box.

house wren 2G0A9598© Maria de Bruyn res         house wren P5181711© Maria de Bruyn res

They do seek out some softer materials with which to line the nest.

house wren 2G0A1982 © Maria de Bruyn res

Carolina chickadees (Poecile carolinensis) make beautiful cups of moss and line them with softer materials – plant fluff or hair from mammals that they find.

Carolina chickadee P3285249 © Maria de Bruyn res     Carolina chickadee IMG_8789© Maria de Bruyn res

Cliff swallows (Petrochelidon pyrrhonota) use mud to construct nests, often underneath bridges and rafters in more urban areas.

cliff swallow 2G0A3239© Maria de Bruyn res     cliff swallow 084A3656 © Maria de Bruyn sgd res

It is well-known that hummingbirds use spider web to help hold their nests together. Blue-gray gnatcatchers (Polioptila caerulea) are also known for doing this.

blue-gray gnatcatcher IMG_8085© Maria de Bruyn res

blue-gray gnatcatcher P4027629 © Maria de Bruyn res

I was surprised a couple years ago to find a nest-building Northern parula (Setophaga americana) also collecting spider web – it appears to be a popular construction material for the birds!

Northern parula 2G0A6727© Maria de Bruyn res

I will leave you with a couple photos from one of my favorite types of nests – that of the white-eyed vireo (Vireo griseus). The first time I saw one being built, I was quite surprised as the birds had chosen a low sapling only about 2 feet from a pathway. They weren’t fond of me watching so I took some photos and left. When I returned some days later, they had completed the nest. (The one below is a different bird.)

white-eyed vireo 2G0A5756© Maria de Bruyn res2

The nests are obviously well-made. This year, I came across an empty nest – also in a low shrub right next to a walking path. It has withstood strong winds, heavy rainstorms and other weather. Now it is a lovely decoration for walkers to see as they pass by.

white-eyed vireo P6125921© Maria de Bruyn res

Next up in the blog series: raising babies!

Some previous blogs about nesting can be seen here and here.

Hopping into springtime

I’ve been planning new blogs for quite some time; then I keep taking new photos that will fit into them and the blog writing gets delayed. But two days ago, I saw such a cool natural event that I resolved to produce a blog quickly and here it is!

One welcome feature of springtime is that many insects emerge from their over-wintering spots. Some are bugs we dislike (mosquitoes, ticks and chiggers), but others are fascinating and wonderful members of our natural systems. Pollinators like this spicebush swallowtail (Papilio troilus) keep our gorgeous plants and important food crops going and many bugs provide other wildlife with meals.

On my trip to Costa Rica last year, our guide not only pointed out birds but also some mammals and insects. He had developed an interest in treehoppers, a group of insects with about 3200 species worldwide that specialize in eating plant sap. He was unable to find any to show me, but I resolved to keep an eye open for them when I returned home. I had forgotten that I had seen my first one the year before, a pretty green Ceresini species.

As I stared at plants during nature walks, I was lucky and managed to find my first treehoppers when I was actually looking for them. These were of a dark-colored species (Acutalis tartarea) that favors the sap of black locust trees, sunflowers, goldenrod and ragweeds.

The treehoppers, which are related to leafhoppers and cicadas, are popular with some entomologists because many species have elaborate “helmets” at the top of their heads. I got to see my first example of this type on my recent walk when I happened to find a young oak tree with numerous nymphs and recently eclosed (emerged) adult oak treehoppers (Platycostis vittata).

The mother treehopper is known for staying close to the nymphs to protect them against wasps and other predators.

The hoppers get plant sap by piercing plant stems with their beaks. The nymphs have extensible anal ducts that deposit the sap away from their bodies. This is important because the concentrated excess sap, called honeydew, can get moldy.

 

                              

The honeydew attracts ants, which like the sugar-rich liquid, so the hoppers and ants have a mutually beneficial relationship.

Just how the helmet develops into an unusual shape has been a source of investigation. One team of entomologists theorized that the helmet was formed by body parts that were actually modified wings. Another researcher countered that this was impossible and that the helmet was an unusual pronotum — the foremost dorsal section of the thorax. More recently, a third group of evolutionary biologists postulated that the helmet is indeed a section of pronotum but one that developed with the aid of genes that code for wings.

In various species, the pronotum has developed into a quite unusual and oddly shaped appendage; examples can be seen in this article. When the helmet resembles a plant thorn, it is thought to aid in camouflage.

When I discovered the group of oak treehoppers, one was just in the process of emerging from its nymph form. A friend who saw the photo remarked that it reminded her of the film Alien but this process was slow and deliberate and not a heart-thumping explosive emergence as shown in the movie.

As you can see, the oak treehopper is quite a beautiful insect with its pristine white body decorated with pink/red stripes and hints of yellow. They made me think of mints and Candy Stripers (a sign of our times when almost anything makes me think of health and health-related concerns. For younger readers: young female volunteers who work under nurses’ supervision in hospitals used to wear pink and white striped smocks and thus got the name Candy Striper).

Not all the adults had the horned pronotum; some had rounded heads.

This close-up of a hopper’s face could evoke all kinds of thoughts. I thought it looked as if it had a pig’s snout. Another friend thought it looked like a grumpy old man. What do you think when you see this visage?

Or about this one, with its head upside down? (It looks a bit more “innocent”, don’t you think?)

In any event, I found these insects just adorable and I felt very privileged to have had the chance to see them emerge into adulthood. It turns out that in this species, older individuals may change color, turning a dull brown or green color. Some mottled forms may be blue with yellowish spots. It would be interesting to see those forms as well one day – or perhaps one of the other treehoppers with a different fabulous helmet!I hope you, too, are able to get out in nature during these social distancing times so that you can connect with the wonderful wildlife around us!

Leapin’ lizards! Remarkable reptiles in Costa Rica

Today is the United Nations’ World Wildlife Day, a time to especially raise awareness about and celebrate the earth’s plants and animals. The holiday was instituted in 2013 to be commemorated on 3 March, the day of the year on which the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) was signed. The theme for World Wildlife Day 2020 is “Sustaining all life on Earth”, which includes all wild animal and plant species as key components of the world’s biodiversity.

To honor this international day of commemoration (and hopefully awareness-raising and action), I’d like to share some of the reptiles that I’ve seen in Costa Rica. But first, let me show you one North Carolina turtle that I saw yesterday and that I don’t think I had seen before. It’s a large turtle called a Florida cooter (Pseudemys floridana), which has a nice pattern with yellow accents on the carapace.

In Costa Rica, we came across one turtle at which we got a good look — a black wood turtle, also called a river turtle (Rhinoclemmys funerea). This is the largest turtle among the reptiles in its genus; individuals can grow to 14 in (35 cm).

black wood turtle

We came across several snakes during our trip in 2019, but a few of them were dead on the road and I decided not to show those. One feisty individual was the cloudy snail-eating snake (Sibon nebulatus); when our guide neared it, the snake reared up in self-defense. Of course, it’s good to remember that most snakes will not strike if they do not feel threatened, as we are reminded by the North Carolina Carolinas Reptile Rescue & Education Center.

 

A snake that I found particularly beautiful was spotted during the 2018 trip in which I participated; our guide spotted it after we had stopped at the side of a road. The neotropical bird snake (Phrynonax poecilonotus), also known as the puffing snake, eats small vertebrates such as small mammals, frogs, lizards and insects, but it is known to have a preference for birds and bird eggs.

These are non-venomous snakes, but they will bite hard when feeling threatened. They also will inflate their neck area in a way reminiscent of a cobra in order to appear dangerous.

The presence of caimans was advertised in various places we visited in Costa Rica but I didn’t see one until a spectacled caiman (Caiman crocodilus) was spotted as we were driving down a highway one day.

This brings me to the various types of lizards I saw. Anoles (Anolis) were in all the areas we visited, Although I couldn’t identify the specific species for several, I enjoyed seeing the differences between them.

 

While searching for birds in a heavily shadowed marshy area, we caught sight of what I thought was a slender anole — obviously a male given its prominent inflated neck flap. However, it turns out that slender anoles have white dewlaps with a small orange blotch so this was a different species.

 

I do believe that this anole was a ground anole (Norops humilis) but would welcome correction if I’m wrong. Their diet includes various insects such as termites, beetles, crickets, termites and flies.

 

 

A somewhat larger reptile than the anoles was the – in my opinion – quite attractive Central American whiptail (Holcosus festivus occidentalis). Like the other lizards that you will see below, they have exceptionally long tails.

Juvenile whiptails have blue tails; their skin patterns are quite lovely, which may account for part of their species name – festivus which means merry or joyous in Latin.

Not much information is available online about these lizards, despite their apparent wide distribution. Some studies have been done about another whiptail genus seen elsewhere that aroused scientific interest because reproduction is by parthogenesis. This has not been reported for this species.

 

The iguanas are the very large reptiles seen in Costa Rica. Despite their size, they appear to be quite agile; it was not unusual to see the large black spiny-tail iguanas (Ctenosaura similis) high up in trees.

The male black spiny-tails can grow as large as 4 ft 3 in (1.3 m), while females are a foot or more shorter. During breeding season, the males develop blue- and peach-colored hues on their jowls, as can be seen in the portrait below, captured by fellow traveler Janet Kurz in 2018.

 

They have been said to be the fastest lizard species, reaching a speed of 21.5 mph (34.6 km/h) in a sprint. Running away is a strategy to avoid predators but they can also bite and lash with their tails if cornered. They are mostly herbivorous, although they will also consume small animals and insects. Unfortunately, they are eaten by humans, some of whom think they can cure impotence.

 

The green iguanas (Iguana iguana) are somewhat smaller than the spiny-tails but they are also large, growing to 4.9 ft (1.5 m) or more. We were lucky to see a juvenile green iguana meander along a smaller tree, posing for quite some time. There might have been others nearby but we didn’t see them. It turns out that these iguanas are quite social – juveniles form pods of about four animals and then spend time grooming one another and sleeping together.

 

 

Their coloring is quite bright but can be other hues such as reddish brown, black, lavender and blue. These iguanas are good climbers, often staying high in trees; reportedly, they can fall as far down as 50 ft (15 m) and still land unhurt.

 

The green iguanas are often found near water and they swim well, being able to stay submerged as long as 30 minutes at a time. Like the spiny-tails, they can use their tails in defense. They can also drop their tails when caught and grow new ones.
 

The basilisks are among the “showiest” reptiles even though they are smaller than the iguanas (e.g., growing up to about 2.5 feet/76 cm in length). They gained the name Jesus Christ lizard because they can “walk” across water when rapidly moving (up to 15 mph/ 24.1 km/h) to escape predators. They have special webbing between the toes on their hind legs and cross the water “standing up” on those legs.

The male common basilisks (Basiliscus basiliscus) have a distinctive fin-like crest on their backs. Both sexes range in color from olive to brown; they are distinguished by a light-colored stripe along their upper lip.

 

The common basilisks also have a stripe along their body, although this fades as they grow older. The females and juveniles look somewhat similar. The females do not care for the young, leaving the eggs once laid. The hatchlings instinctively know how to care for themselves.

 

 

The green basilisk (Basiliscus plumifrons) is also known as the plumed basilisk. Males have three crests (on the head, back and tail), while females (shown in the photos here) only have a head crest. The juveniles have no crests.

 

Like the other basilisks, these lizards can dive under water after running along the surface for a time. They can stay submerged up to an hour but often do not do this as they could fall prey to aquatic predators.

 

 

Like the common basilisks, the green basilisk females leave their eggs and the newly hatched babies are able to run, climb and swim right after birth.

Among the brown basilisks (Basilicus vittatus), also called striped basilisks, the juveniles (shown below) can often run further across water than the adults.

   

The crests are similar to those in other species. These basilisks have dark bars across their backs and quite yellow stripes.

Like the other basilisks, these lizards often eat insects but also eat berries and other fruit, making them omnivores.

 

The last type of lizard in this reptile review is another iguana known by a couple popular names: the casque-headed lizard or the smooth helmeted iguana (Corytophanes cristatus).They have several distinct features that make them quite unique.

They are characterized by very long toes, a long tail like the other lizards and highly variable coloration, ranging from olive, grey, black, brown to reddish-brown, often with irregular blotches of other color.

 

 

 

They are also able to change their color rapidly as a form of camouflage. Unlike the other lizards, they tend to freeze in place when predators approach (a strategy called catalyptic freezing). If this and trying to appear larger by erecting their crest and expanding their gular pouch do not scare off predators, they will bite and attack.

 

 

 

They differ from the other iguanas and basilisks in that they often do not actively seek out prey. Rather, they sit and wait for worms, other lizards, insects and spiders to wander by and then pounce on them.

One final noteworthy and unexpected fact: because these lizards sit still for very long periods of time, both a fungus and a plant have been found growing on their skin!

Happy World Wildlife Day!

 

Awesome amphibians in Costa Rica

During my two trips to Costa Rica (so far?), it was my good fortune to see different kinds of animals besides the birds which were the focus of the trips. There are a lot of interesting amphibians and reptiles to see; in this blog, we’ll see some of the amphibians that I managed to photograph. I was ultimately able to identify almost all of them except the one to the right; if anyone can tell me which frog this is, it would be appreciated!

 

One of the most famous frogs in the country is the little (0.75-1 inch) strawberry poison dart frog (Oophaga pumilio), also known as the blue jeans frog because many individuals have a bright red upper body accented by a bright blue lower half. It turns out that the species has an estimated 15-30 color variations – in 2000, totally blue individuals were seen at the La Selva Field Station.

The female lays 3-5 eggs on a leaf and the male then keeps the eggs hydrated with water he transports in his cloaca. After the eggs hatch and tadpoles emerge, the female frog transports them on her back and deposits each one separately in a small pool formed in the crevice or hole of a tree or a large bromeliad. There, the tadpoles consume only unfertilized eggs that their mother feeds, a practice called obligatory oophagy,

 

The feeding habits of the adults (certain ant and mite species) are what makes them poisonous when touched or eaten. Their skin is toxic and humans should wash their hands vigorously after touching them.

A very tiny frog that we saw last year was the common tink frog (also called dink frog; Diasporus diastema). I’m not absolutely certain that the two shown below are tink frogs but think they are. These tiny frogs change color, having grayish brown skin with spots or bars during the day and a pale tan or pink color at night, when it is most active.

 

 

A somewhat larger amphibian that we saw at the same pond as the tink was the hourglass tree frog (Dendropsophus ebraccatus). Part of the species name comes from the Latin term ebraccata, which means “without trousers”. Some people call this frog the “pantless frog” because they think the smooth yellow thighs that contrast with its highly patterned back make it look as if it is not wearing pants. These individuals had patterns on their thighs, however!

The attractive hourglass frogs were in an amorous mood when we spotted them. The female chooses her mate and he mounts her to deposit his sperm. She then will seek out a suitable place for her eggs, either in the water or a leaf overhanging water. When the arboreal eggs hatch, the tadpoles roll off the leaf into the water below.

These frogs are of interest to scientists because their skin contains bioactive peptides which have anti-fungal and anti-bacterial properties and might even have therapeutic properties useful in treating diabetes.

 

The pond had quite a few frogs in residence and several brilliant forest frogs (Lithobates warszewitschii)were among them. They are slender-looking frogs with pointy heads. Their sides are apparently always darker in color than their backs.

 

 

Their coloring seems to vary somewhat, being browner in some individuals and featuring more green highlights in others. They tend to have yellow spots on their legs.

They do not have vocal sacs or slits but do make trilling sounds.

 

 

We were lucky to catch a glimpse of a red-eyed tree frog (Agalychnis callidryas) at the pond. Although some lodges will ask you to avoid using a flashlight during night-time walks to see amphibians, it’s very difficult to spot them without some use of a light. That’s how we managed to spot the tree frog.

We came across the Canal Zone tree frog (Boana rufitela) taking a daytime nap, right out in the open on a large leaf next to a walking path. This frog is also known as the red-webbed or scarlet-webbed treefrog. It used to have the scientific name Hypsiboas rufitelus, which was changed for a reason I couldn’t determine.

The smoky jungle frog (Leptodactylus pentadactylus) is Costa Rica’s largest frog species; males grow to as much as 7.3 inches (18.5 cm). The adults are so big that they can eat small mammals (e.g., bats), small birds and lizards. They have some interesting characteristics. In contrast to the little blue jeans frogs, who only lay 5 or fewer eggs, female smoky jungle frogs lay about 1000 eggs at a time! They can secrete copious amounts of mucus, which makes them difficult to hold for predators; in addition, these secretions are toxic. They can even vaporize the toxin, causing people to sneeze and get swollen eyes.

What has further contributed to making them famous is the alarm call that they emit when captured; some liken it to a human person screaming. It doesn’t sound like that to me; rather, what I heard in a video sounds to me like a sound that a distressed cat might make.

That brings us to Costa Rica’s largest amphibian, the cane toad, also known as the marine toad. They are not only this Central American’s biggest amphibian, though; they are the largest toad in the world, growing as long as 9 inches long (22.86 cm) and weighing up to 3.5 lbs (1.59 kg).

This animal has also gotten a new scientific name; while it used to be called the Bufo marinus, it is now known as the Rhinella marina. Like some of the frogs, this toad has toxic skin and they are especially dangerous for dogs.

They were introduced to different countries to control pests as they have voracious appetites. Now they are considered an invasive species and pests themselves.

In 2018, I came across these toads in different places. There are a few living around a fountain in the hotel in San José where our tour groups stayed; they enjoy taking a shower under the running water.

To end today’s offering, I’ll show you the frog that really fascinated me most — the reticulated glass frog (Hyalinobatrachium valerioi). Our guide, Cope (who showed us the awesome spectacled owls and bats shown in previous blogs), led us to this awesome amphibian. It has a green and yellow back but its ventral (abdominal) skin is completely transparent! The frog’s heart is covered by white tissue and its liver and digestive tract are also white. Here you see the male frog on a leaf guarding eggs – he actually looks pretty much like the egg masses!

Isn’t nature endlessly interesting? Next blog: Costa Rican reptiles!