The russet-backed oropendola (Psarocolius angustifrons) is one of the most common and widespread of the oropendola passerine birds in the Amazon. They are mostly dull brown with rufescent rump and olive tone to head. This species has three subspecies: P. a. astrocastaneus, on the western Andean slope; P. a. alfredi in the eastern Andean subtropical forest; and P. a. angustifrons in Amazonia. These subspecies differ primarily in bill and face coloration and vocalizations. During the breeding season, they are seen arduously building their characteristic basket-like nest that hang from tree branches in riparian and second-growth habitats. These closed nests keep their eggs and chicks protected from predators.

Russet-backed oropendola (Psarocoliusangustifrons) and violacious jay (Cyanocorax violaceus) scaring away intruders. PC: Tom Matia

The violaceous jay (Cyanocorax violaceus) is a colorful and gregarious member of the crow family of northern South America. This jay species is predominantly dark violet-blue, with a black facial mask. The violaceous jay can be found in a variety of forest habitats, including degraded forest, but is especially common along riparian corridors and forest edges. They are omnivorous and can be seen eating fruits, insects and bird and reptile eggs.

A great contrast is easily noticed between the species: some think that the call of the russet-backed oropendola sounds like water drops, while that of the violaceous jay strikes some as similar to a car horn. The species also have similarities: they are conspicuous resident and widely distributed species in the Amazon.

Brown capuchin (Cebus apella) might look cute but
they are fierce predators. | PC Claudia Rohr

These species have something else in common: confrontations with brown capuchin monkeys! Brown capuchins (Cebus apella) feed mostly on fruits and invertebrates, but from time to time enjoy a meal of bird eggs and chicks. Quite often, a group of these monkeys can be seen climbing up the trees right outside the office at Los Amigos, where the oropendolas and jays are nesting close to each other. When the brown capuchins arrive, adults of both bird species first make their presence known with their characteristic calls. When the monkeys draw close to the nests, the oropendolas and jays cooperatively try to chase them away. These encounters conclude with either the monkeys leaving empty-handed or the birds suffering broken nests and lost eggs.

The striking cooperation between these bird species is short-lived. Jays will try to take eggs and chicks from other bird nests, including fiercely defended russet-backed oropendola nests.  For the oropendolas and violaceous jays, the expression “the enemy of my enemy is my friend” is applicable only when the common enemy is visible.

Solitary sandpiper (Tringa solitaria) unlike other sandpipers and other migratory birds, do not migrate in large flocks and can be found along the banks of shady creeks. PC: Alex Wiebe

Movement is an essential part of our day-to-day lives. However, this is not only true for us; most species are constant on the move. For some, this is due to continuous changes in their surroundings and others because of their ecology. Most of these movements go unnoticed by us, however, there is one that does not: Bird migration. If you look up into the sky at this time of the year, you may notice the unusually high number of birds flying around. For birds that migrate, they do so twice a year, between their breeding homes habitats and their nonbreeding grounds. Some migrations are large-scale like the Artic tern (Sterna paradisaea) which incredibly manages an annual round-trip of 70 000 km. Others are much shorter, such as altitudinal gradient migration along the Andes.

Migration is the seasonal movement from one region to another influenced by a series of factors. Specifically, bird migration is strongly influenced by the availability of nesting sites and food. In temperate zones, the hours of increased light during the summer allows birds to forage for longer periods. Additionally, because of the lower biodiversity, competition for resources and nesting sites is not as intense. These are appealing conditions to use temperate zones as breeding sites. Yet, as the season ends, food availability and the hours of light decrease, and birds have to find suitable grounds for the rest of the year. The tropics, despite the food abundance throughout the year, are not attractive to some species as breeding grounds because of the intense competition for resources and nesting sites due to the great biodiversity. However, most of these species become temporary residents of the tropics until is time to breed again.

Out of all the bird species in the world 40%, or around 4 000, are regular migrants. However, they are unevenly distributed around the world. In countries in the far north like Canada and Scandinavia, birds migrate southwards during the boreal winter to flee the harsh winter and will only go back until the following spring.

Chivi Vireo  (Vireo chivi) is one of the most widespread and common passerines of South America. This species consists of a complex mosaic of resident and migratory populations. During the austral and boreal winter, there is a seasonal overlap between the resident population and wintering population from the temperate zones.  PC: Alex Wiebe

Migration can take several weeks. Because of this, birds enter a state called hyperphagia before their journey. During this state, they will ingest as much food as possible to build up the fat reserves that will provide them with the energy needed for their journey. Once the migration has started, birds use a combination of senses and cues that are not fully understood, to reach their destination. They can orientate themselves by sensing the Earth´s magnetic field, and by the position of the sun, stars, and landmarks seen during the day. Species do not migrate all at once or in the same way. This is why you can see migrating flocks or individuals at different times of the day and for several months. Each species starts its migration at a specific time and some vary their migration year to year depending on food availability. The beginning of migration is also influenced by changes in the length of daylight. First-time migrators often make the journey on their own, despite the fact that they have never been to their winter home before. Impressively they are able to find them.

To avoid exhaustion and starvation during the thousands of kilometers flight, birds stop to recharge their energy along the way. However, by doing so, they are vulnerable to fall victim to predators. While enduring their journey, migratory birds face further threats like wildfires and storms, which appear to be intensifying due to our changing climate; shortages of resting areas, due to human encroachment; disorientation by city lights; and obstacles such as tall buildings. In 1971, The Ramsar Convention on wetland was agreed as a measure to protect migratory birds. However, each year the population of migratory birds decreases due to habitat loss and degradation in the tropics. By protecting the tropical forests, we are ensuring the well-being of migratory birds and ensure that future generations have the opportunity to this spectacle.

For further reading:

• Salewski, V. & Bruderer, B. (2007) The evolution of bird migration-a synthesis. Naturwissenschaften 94:268-279.
• Robbins, C., Sauer, J., Greenberg, R. and Droege, S. (1989) Population declines in North American birds that migrate to the neotropics. Population Biology Vol. 86, pp. 7658-7662.

Bluish-fronted jacamar (Galbula cyanescens) located in bamboo at LABO. PC: Tom Matia

At the time of my encounter, I did not realize the rarity of the event. I was walking across an old channel of the Los Amigos River that is in its early successional stages. There are no tall trees, instead, there are many shrubs covered in vines. Bordering this channel are the towering trees of the floodplain forest, making this edge habitat an ideal location for a Tiny hawk (Accipiter superciliosus) (Global Raptor). I had just walked past a resting bluish-fronted jacamar (Galbula cyanescens) when my eye caught a glimpse of a bird careening through the vegetation. I followed the shadow through the vegetation and, in the clearing that the trail made behind me, watched a small flying raptor raise its feet forward and pin the bluish-fronted jacamar to its perch.

A photo taken through binoculars of the Tiny Hawk after pinning the jacamar to its perch. PC: Tom Matia

The small raptor (22-28cm/8-11in) is known to be a specialist at predating on avifauna and had the jacamar in its grip (Global Raptor). It seemed the attack would prove fatal as there was hardly a fight from the jacamar. The hawk soon took notice of my presence and, not wanting to disrupt its natural behavior and its success, I walked away from the scene. A few hours passed by the time I returned to investigate the scene; there was not a feather or scrap to be found. This could mean two things, the jacamar made it out the talons of the tiny hawk, however, due to the elongated nature of their talons, I choose to believe that the later, the jacamar left the scene in the grasp of the hawk.

When I returned to eat dinner, I learned that little is known about this species of raptor and that the sighting was very rare! Looking further into this species, I discovered that there is hardly any information on their populations. With the help of citizen science, specifically from eBird by Cornell University, I found that only 130 observations have been recorded in Peru over the past ten years. With such little documentation on this uncommon bird, it is alarming that they are estimated to lose 19-24% of suitable habitat in the next twenty-two years (BirdLife).

The Tiny hawk has an assumed population of 670-6,700 individuals and is currently listed as ‘least concern’ by the IUCN, and BirdLife, due to its expansive range (BirdLife). Hearing these statistics shocked me and I immediately searched population sizes of species that are rare to see. The jaguar (Panthera onca), an animal that is incredibly elusive, yet possibly more likely to be encountered, has roughly 15,000 individuals according to the WWF (Quigley). And so I thought, “a tiny hawk is not something you see every day”.

References:

Global Raptor Information Network. 2018. Species account: Tiny Hawk Accipiter superciliosus. Downloaded from http://www.globalraptors.org on 15 Sep. 2018
BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/09/2018.
Quigley, H., Foster, R., Petracca, L., Payan, E., Salom, R. & Harmsen, B. 2017. Panthera onca(errata version published in 2018). The IUCN Red List of Threatened Species 2017. Downloaded on 15 September 2018.