22 Apr 2016

Sky Heritage: Wild Birds in Panama City (II)

These birds, as immigrants to this country, have settled down here and have since legalized their status: they are now Panamanians!   R. Ridgely mentions that they were supposedly brought from Colombia as caged songbirds, and that they were first seen in the Balboa area (in the area formerly known as the Canal Zone or the “Zone”), around 1932 (3: Pg. 356). 

The current geographical distribution range of this bird goes from the south of Mexico to El Salvador and Honduras; and from Colombia to the Guianas and the north of  Brazil; from there to the south of Brazil, along the coastline; the Lesser Antilles, and introduced in Central Panama.  In Panama, its distribution range has expanded over the years.  Presently, it goes beyond the “Zone” towards parks and wooded areas in Panama City, and to some other areas. If we pay attention, we will discover that these birds do not like concrete or lack of vegetation.

Its name in Spanish, “sinsonte”, comes from the word cenzontle, “bird of four hundred tongues” (originally centzontli in the Nahuatl language).  Its genus name (Mimus) means “mimic”, an ability that the approximately 30 species of this family (Mimidae) can really master. Species found in Panama City have definitely earned their Mimus name.  

Their song is based on repetitive phrases with occasional single notes, very similar to the song of the clay-colored thrush, capisucia or cas-cás (Turdus grayi), which is more commonly found in the city, except that the song of the latter is based on single notes only, not phrases, and can be heard very early in the morning or in the afternoon, but only during breeding season.  The song of the tropical mockingbird, however, can be heard all year round, any time of the day.

Being a good singer has its advantages.  For example, it is a helpful skill during mating season.  Unfortunately there are some disadvantages too: people capture and cage tropical mockingbirds because of their musical talent, and then they become prisoners for life.

They forage for insects and fruits on the ground, and they can really run! When they run, they would suddenly stop and raise their short, round wings.  They take care of young birds collectively; it means, they take turns.  When on duty, tropical mockingbirds take care of their own offspring and those of their fellow birds.

Mr. Félix Bolaños, resident of Villa de las Fuentes, in Bethania, has succeeded in introducing and re-introducing this and other bird species in different areas of the city. In his farm at Loma del Río, in Chepo, he freed two tropical mockingbirds (a couple) 18 years ago, and they are still reproducing.  In his property in Panama City, he freed another pair, and they would go back to his yard every day to feed on fruits. They also produce offspring twice a year.  “Their mating season goes from February to April, and from September to November” – as confirmed by Mr. Bolaños (8).

This protector of our winged treasure also told me that, in the 50’s and the 60’s, there were two famous tropical mockingbirds in Panama City.  One of them learned to sing the Panamanian folk song “Guararé”: that was the mockingbird at Café Coca Cola, a place that is still operating in Santa Ana. Another one, which was somewhat more versatile, was able to hum Schubert’s wedding chords, “La Cucaracha”, and other tunes.  This was the tropical mockingbird of Farmacia Cristo Rey, no longer operating, that was located in the corner of the 34th Street and Avenida Cuba.

The Clay-colored Thrush (Turdus grayi)

The cas-cás or clay-colored thrush is probably one of the most known birds in Panama City.  Both male and female are very similar in appearance.  However, we must differentiate them from the female great-tailed grackle, for the female is larger in the latter species. 

The foundation of their nests is made of clay.  The female clay-colored thrush gathers materials for the nest and, little by little, takes the materials to the nest.  On top of this foundation, which can be placed up in a tree or under eaves, the female places sticks, leaves and clay. It is not an utterly attractive bird, but it really can sing!  In addition, it is one of the most studied birds in the country, and it also is the national bird of Costa Rica.

All the individuals from this species, on a particular location, breed simultaneously. Therefore, during the dry season (February and March) their songs can be heard all over the city, signaling that mating season is about to start for Panamanian birds.   A popular saying suggests that the clay-colored thrush sings as if “calling for rain”, just because it does not sing other than during this season. In fact, however, male birds sing when they are “in love”.

Why do they sing that long? It is one of the marvels of nature. As with many other species, the female clay-colored thrush chooses her mate. Thus, male birds compete through their songs. The bird who sings the best and the longest has higher chances of reproducing.  They start singing very early, in unison, even before breakfast! After listening to their songs, then female birds decide.

A clear advantage of breeding during the dry season is that food is abundant. There is plenty of fruit from the velvet tree or “dos caras” (Miconia) and the gumbo-limbo or “cholo’pelao” (Bursera) tree, among others, which helps male individuals endure those extended singing sessions.  The season makes it possible to eat very quickly and go back to singing. Sexual selection has a direct effect on the time for breeding.

Biologists have been studying this species in Panama for several decades now (9). It has been reported that the breeding season starts in January in the Pacific coast as it gradually moves to the Caribbean coast.  Having said this, breeding season can start a month later in the Summit park area, only 20 km away from the coast, but would start in mid-April in the coastal areas of Colon.  There are no reports of such a time difference for the start of breeding season within one species, and within an 80 km range, for any birds in cooler regions.  

Some biologists, based on their studies in Panama, say that the availability of food (which allows for egg production and the development of young birds) may not be the most important factor for tropical birds.  For some species, it is. However, in some other species, evidence shows that sexual selection is still the most decisive factor. Such is the case of the cas-cás.

Migration of Predatory Birds in the City

The remains of a stork found in Meklenburg, Germany on May 21, 1822 showed that an arrow through its neck had been the cause of death.  Due to the fact that arrows were last used in Europe many years before the finding, there was one strong possibility for the origin of the arrow: Africa.  Certainly, researchers did confirm the arrow had an African origin. Additionally, this proved that storks spend their boreal winter in Africa.

The first formal studies on bird migration ever recorded were conducted by Swedish naturist Carl Linnaeus.  However, if it had not been for Danish Master Hans Mortensen who, in 1899, had the idea of identifying birds with numbered rings on their legs, we would have not known so much about migration as we do today.  Since then, bird migration has been thoroughly studied, thanks to this method. Birds are captured, rings are placed, and then they are freed again. Eventually, when birds are watched and recaptured in other regions, ornithologists retrieve the information and are able to unveil their migration patterns.

According to the records, 15% of birds in Panama (i.e. 140 out of a total of more than  950 species) are migratory birds. They do not nest here, and they can only be seen during a certain period of the year: winter in the Northern Hemisphere.  Many of them just fly through Panama for their migration voyage, heading south of the continent, and when they go back north.  Other birds stay in the country. Some others arrive here earlier and leave later, these may stay longer in Panama than in their regions of origin.

Since the American continent gets narrower in Panama, a great number of bird species can be spotted at the same time during their seasonal migration. Many travel along the Pacific coast, especially on their way south. This migration reaches its peak, in number of birds, from late September to early November.  This route turns Panama into one of the few places in the world where you can see, at the same time, several species from the three main migratory bird groups: birds of prey, waterfowls, and songbirds.

Every year, during the months of October and November, almost every individual from the two main species of hawks: Swainson’s hawk (Buteo swainsoni) and the broad-winged hawk (Buteo platypterus), in conjunction with the turkey vulture (Cathartes aura) and other raptors, fly along a narrow corridor along the Pacific coast in Panama.

Years of research led by Neal Smith, ornithologist of the Smithsonian Tropical Research Institute, showed decades ago that this bird migration amounted to several hundred thousands of individuals every season, and that this raptor migration was one of the most spectacular migrations in the New World, and one that can be easily observed.  According to bird counts conducted by Smith between 1970 and 1982, up to 981,000 birds were spotted in 1982 (10).

Sixteen years later, a simultaneous count led by George Angehr, also from the  Smithsonian and the Audubon Society, raised the total count to 1.6 million predatory birds.  “Simultaneous counts in different regions of the country help find out the times and routes used by migrating raptors”, said Angehr.

In 2005, in what was known as “the first global study on transcontinental raptor migration: from ocean to ocean”, more than 40 volunteers from the Audubon Society of Panama, the Smithsonian Institute, Universidad de Panamá, along with residents of rural communities, and volunteers from  Canada, Argentina, Mexico, and the U.S., provided detailed information about the migration of birds through an environmental corridor traversing Central Panama.  Count results showed that approximately 3 million raptors flew over Panama on their way south during the migration of 2005.  This amazing figure is even more impressive if we take into consideration that migrations of more than 1 million birds only happen in three other places in the whole world (Costa Rica, Mexico, and Israel) (11).

In addition, this migration is one of the few cases in America where raptors cover long distances during long periods…without even stopping for food! Using a soaring flight technique, hawks and turkey vultures take advantage of raising air currents as thermals, edge of storms, and slope winds as means of propulsion.  This helps them conserve energy because, in contrast with other birds, they would not able to cover long distances if they had to be constantly flapping their wings.

If night comes while they are flying over Panama City, they would find a resting place on the woods west of the Panama Canal area and on the Metropolitan Natural Park.  If the following day is a rainy or cloudy day, they would not fly due to the lack of warm air currents. If bad weather lasts for a few days, they would remain on the woods the whole time.  Few of them would fly over the city. When a sunny day finally arrives, they will leave, thus thousands would be seen swirling around and letting thermals carry them away on their eastbound journey.

While the turkey vulture (Cathartes aura, 71-81 cm) is the largest of migratory raptors in tropical America, its travel companions have a rather medium size.  The Swainson hawk (Buteo swainsoni, 44- 52 cm) travels from North American plains to similar regions in South America.  Some of them stay along Central America, but hundreds of thousands continue their journey to distant places like Argentina (after traveling for almost 7,000 miles).

Birds that fly over Las Cruces, New Mexico, during the first days of October arrive to Panama 18 days later, and reach Argentina during the first week of November. The broad-winged hawk (Buteo platypterus, 38-46 cm) flies over Texas late September and arrives to Panama 12 or 14 days later.  Part of the population remains here, and the other fly to different regions in South America.  I would like to mention that, besides the population of turkey vultures (Cathartes aura) that visits Panama during migration season, we also have a resident population all year round.

In the dry season (between March and April), these three types of birds will return to North America. This time, however, their crossing through Panama may last just one day (in contrast to three days coming south), because the northern wind during dry season allows them to glide and soar faster.

On his comprehensive General and Natural History of the Indies (Historia General y Natural de las Indias, ca. 1520), Fernández de Oviedo was the first European to record these migrations, based on observations of birds in Panama (specifically, birds coming back from the south of the continent, along the Caribbean). Fernández de Oviedo reported: “For many years now I have seen the sky full of birds, very high above, during the month of March.”  Fortunately, five centuries later, all these natural wonders have been revealed to the general public.  

Even a couple of years ago there were few people (non specialists) who knew about or were interested in this seasonal occurrence. We better look up to the sky between October and November…more people do it now every year. If we do, we will be able to marvel before the raptor migration once properly described by an observer as a “river of birds.”  As one colleague said, we could be watching all the parades during the national holidays in the city, and up in the sky these migratory raptors would be saluting also and will provide us with a spectacular natural parade on their way south.

One last comment…

My intention with this article is to highlight the importance of wild birds in the city, their relation with humans, and how valuable their presence is.  The only way of fighting the ill-planned development we are now facing, a development which only favors the commercialization of the world, is by taking a critic approach.  This can be accomplished through education, understanding, and by being appreciative of the world around us.

In this particular moment of the history of Panama City, we can protect ourselves by protecting those “other inhabitants” with which we share our environment. For the appreciation we have for them, for their constant presence in the city, and for representing the beauty and poetry of life more than any other species, let us please show wild birds the respect they truly deserve.

 

(8) Félix Bolaños, personal message  2003

(9) Refer to: Dyrcz, Andrzej. 1983. Breeding Ecology of the Clay-Colored Robin Turdus grayi in Lowland Panama. Ibis 125(3): 287-304

(10) Smith, Neal G. 1973  Spectacular Buteo Migration over the Panama Canal Zone, October, 1972. American Birds 27(1): 3.

Smith, Neal G. 1980 Hawk and Vulture Migrations in the Neotropics. In: Keast, Allen and Morton, Eugene S. (Ed.), Migrant Birds in the Neotropics: Ecology, Behavior, and Conservation: 51-65. Washington, D.C.: Smithsonian Institution Press.

Smith, Neal G. 1990 Soaring Raptor Migration Through the Isthmus of Panamá. In: Olsen, Ian Newton and Penny (Ed.), Birds of Prey: 155-164. New York: Weldon Owen Ld.

(11) Ventocilla, Jorge  2002  A “river of birds” flows in Panamá. Otros Habitantes, La Prensa newspaper, October 20, 2002, P. 5B.