Tyrannus savana

Geographic Range

Tyrannus savana is a native species of southern Mexico to countries as far as Argentina in South America. Most Tyrannus savana inhabit and breed in grasslands and open terrains of these countries and do not migrate (Jahn & Tuero, 2013). Some but not very many Tyrannus savana do migrate and the ones that do have been known for their standard migration towards northern areas of South America like Venezuela and Colombia during the months of June, July, and August these three months are the South American winter season (McCaskie and Patten, 1994). Some subspecies of Tyrannus savana have been recorded and cited as vagrants. These are individuals that have migrated out of their comfort zone as far as the northern United States and southern Canada in the months of September and October. (McCaskie and Patten, 1994). There is little available information about the Tyrannus savana being an introduced species in other countries.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

The species Tyrannus savana is found in many open habitats. A majority of them are found in terrestrial habitats, mainly savannas. Other open habitats Tyrannus savana are found in are: second growth forests, riparian forests, pastures/agricultural lands, marshes, seasonally wet grasslands, mangroves and even in open urban/residential areas (Teul, Piaskowski & Williams, 2007). The Tyrannus savanna are usually found at elevations between 0 to 4100 m (“Fork-tailed flycatcher – Tyrannus savana - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2012). Some individuals of Tyrannus savana in some cases prefer to nest in open tropical savanna habitats rather than closed ones with higher tree densities. During migration Tryannus savanna are usually found in their preferred habitats but are also open to exploring other new habitats like tall humid forest canopies. (Jahn & Tuero, 2013).

• Habitat Regions
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland

• Wetlands
• marsh marsh

• Other Habitat Features
• urban urban
• suburban suburban
• agricultural agricultural
• riparian riparian

Physical Description

Both sexes of adult Tyrannus savana have equivalent body masses and weigh between 28 to 32 grams. Adult males are longer than adult females length-wise because of their longer tails, they have a length measurement of 37 to 41 cm (“Fork-tailed flycatcher – Tyrannus savana - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2012). Short-tailed females have a length measurement of 28-30 cm. The Tyrannus savana has the longest tail compared to body size of any bird on earth. For males the tail is 2 to 3 times longer than the length of the body (“Fork-tailed flycatcher – Tyrannus savana - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2012). Its wingspan measures 38 cm at most (Paul Lehman, 2009). Adult males and females have similar coloration; however, some males may have a yellow crown stripe found on their black caps. For males and females the color of the feathers are pale gray, breast color is white, and they both have black caps, (“Fork-tailed flycatcher – Tyrannus savana - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2012). Its eye color is brown. Juveniles have gray caps, brown backs, and cinnamon colored feathers (Jahn & Tuero, 2013). There are a few geographic variations for subspecies of Tyrannus savana . One subspecies Tyrannus savana monachus has a darker gray back compared to the subspecies Tyrannus savana sanctaemartae , whose lighter gray back contrasts with its black head (Jahn & Tuero, 2013). Little is known on seasonal variation between subspecies and polymorphisms in Tyrannus savana . Some polymorphisms are known in different Tyrannus species like Tyrannus tyrannus (McKitrick, 1990). A cousin to Tyrannus savana is Tyrannus forficatus , they differ from each other by Tyrannus savana having a longer tail. The Tyrannus forficatus also has a white terminal band on their tails while Tyrannus savana does not (Jahn & Tuero, 2013). There is little available information about the basal metabolic rate of Tyrannus savana . Some information for basal metabolic rate has been found in a closely related species Tyrannus tyrannus , which is 0.44 W and may be similar to the basal metabolic rate of Tyrannus savana (“Eastern kingbird –Tyrannus tyrannus – Encyclopedia of Life,” 2010).

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry
• polymorphic polymorphic

• Sexual Dimorphism
• male larger

Reproduction

There is little available on the reproduction mating systems of Tyrannus savana (Jahn et al., 2014). However, in its closely related cousin Tyrannus forficatus and other species in the Tyrannidae family the mating systems have been found to be monogamous (Regosin and Pruett-Jones, 1995). This means that one male and one female mate at a time. Although, little information was available for the mating system of Tyrannus savana it can be assumed that like its cousin Tyrannus forficatus and other Tyrannidae species Tyrannus savana also mate monogamously (“Scissor-tailed flycatcher – Tyrannus forficatus - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2013).

• Mating System
• monogamous monogamous

There is little available information on Tyrannus savana breeding intervals. However, for other species of the Tyrannidae family like the Tyrannus tyrannus , they are found to breed once a year (“Eastern kingbird – Tyrannus tyrannus - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2012). It can be assumed that as Tyrannus savana breed seasonally per year and that they also may have a breeding interval of once a year ("Fork-tailed Flycatcher," 2008). The breeding season of Tyrannus savana varies greatly depending on which country in South America they are located in. In Belize and Colombia Tyrannus savana seasonal breeding takes place starting around February to May. In Panama, Tyrannus savana have been found to promote mating displays in January and build active nests for laying eggs around February to June. Migrants of Brazil have been found to seasonally breed between late September and February. Some subspecies of Tyrannus savana like Tyrannus savana savana have been found to migrate to Venezula and seasonally breed from March to mid-October. In Argentina, Tyrannus savana have been found to seasonally breed from October to March (Teul et al., 2007). Eggs laid by Tyrannus savana have been found to average between 2 to 3 eggs with the highest laid eggs to be 4 and the lowest laid eggs to be 1 (Teul et al., 2007). There is little available information on Tyrannus savana time to hatching. However, it has been found in its cousin the Tyrannus forficatus that the average time to hatching takes 14 days (“Scissor-tailed flycatcher – Tyrannus forficatus - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2013). It can be assumed that like its cousin the Tyrannus forficatus , the Tyrannus savana may also have a similar time to hatching time. There is little available information on Tyrannus savana birth mass. There is also little available information on birth mass on other species from the Tyrannidae family. The Tyrannus savana has a fledging time of leaving the nest at earliest of 13 days and latest of 16 days ("Fork-tailed Flycatcher," 2008). There is little available information on Tyrannus savana independence time. However, it has been found in another relative of the Tyrannidae family the Tyrannus tyrannus it turns out that 30 days are the average for their independence (Murphy, 1996). It can be assumed that the average independence time in Tyrannus savana takes around 30 days or so as well. There is little available information on female Tyrannus savana reproductive age. However, in its cousin Tyrannus forficatus it has been found that its female reproductive age is 1 year (“Scissor-tailed flycatcher – Tyrannus forficatus - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2013). It can be assumed that female Tyrannus savana have a similar age of reproduction around one year. There is little available information on male Tyrannus savana reproductive age. However, in its cousin Tyrannus forficatus it has been found that its male reproductive age is 1 year (“Scissor-tailed flycatcher – Tyrannus forficatus - IUCN Red List (Species Assessed for Global Conservation) – Overview,” 2013). It can be assumed that male Tyrannus savana have a similar age of reproduction around one year.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Like many other bird species in the Tyrannidae family Tyrannus savanna is found to care for their young, also known as altricial parental investment (Jahn, et al., 2014). Female Tyrannus savanna have been known to provide the most parental care to their young (Teul et al., 2007). There is little information available on Tyrannus savana pre-fertilization. However, in their closely related relative Tyrannus tyrannus it has been found that female Tyrannus tyrannus are mainly responsible for pre-fertilization protection (Murphy, M., 1996). It can be assumed since female Tyrannus savana largely provide for their young they most likely also provide protection at pre-fertilization. At pre-hatching/birth female Tyrannus savana have been found to provide the most provisioning and protection of their chicks from other predator birds (Teul et al., 2007). There is little information available on Tyrannus savana pre-weaning and pre-independence. However, in their closely related relative the Tyrannus tyrannus it has been found that both males and females still provide provisions and protections in the young stages of pre-weaning and pre-independence (Murphy, M., 1996). It can be assumed that both male and female Tyrannus savana may possibly provide care for their young at their pre-weaning and pre-independence stages of their life span.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female
  • protecting
    • male
    • female

Lifespan/Longevity

There is little information available on the longest known lifespan and expected lifespans of Tyrannus savanna in the wild and in captivity (Jahn & Tuero, 2013). There is also little information available on lifespans of other species in the Tyrannidae family in the wild or in captivity.

Behavior

The Tyrannus savana are known to be arboreal species that are usually found on low levels like fences, powerlines, and branches of trees and shrubs (Jahn & Tuero, 2013). Depending on the population and subspecies of Tyrannus savana they are found to be either fully or partially migratory. Northern populations are found to be sedentary and permanent residents with little to some local and nomadic movements. Southern populations are found to be partial to full migrators who migrate towards the central and northern parts of South America during the South America winter season known for occurring in the months of June, July and August. Western and Eastern populations are for the most part sedentary permanent residents. The Tyrannus savana is generally an early spring and fall species who only migrate throughout South America known as austral migrants (Jahn & Tuero, 2013). However, quite of few of its subspecies have been known to migrate vagrantly outside of South America, throughout the countries of Mexico and North America and have been found to migrate as far as southern Canada. Sedentary Tyrannus savana are usually found in pairs or family groups. While nesting Tyrannus savana like other members of the Tyrannidae family are known to be aggressive defenders when it comes to defending nests and territories against conspecifics. During migration, season breeding and non-season breeding Tyrannus savana are generally found in large colonial flocks consisting of thousands of individuals. During flight Tyrannus savana are also known to mix in with Tyrannus tyrannus flocks. Even during migration they also actively chase away conspecifics or other bird predators (Jahn & Tuero, 2013). The only known information for sexual behaviors in Tyrannus savana is as males call they usually preform an aerial display consisting of spirals and somersaults (Jahn & Tuero, 2013).

• Key Behaviors
• arboreal arboreal
• flies
• diurnal diurnal
• crepuscular crepuscular
• motile motile
• nomadic nomadic
• migratory migratory
• sedentary sedentary
• territorial territorial
• social social
• colonial colonial

Home Range

There is little information available on the size of the Tyrannus savana home range as there is little information available on home range sizes in other species of the Tyrannidae family.

Communication and Perception

There is only a few sources of information about Tyrannus savana communication. One source is that they mainly communicate through vocals. The Tyrannus savana can make a variety of vocalization noises like dry, sharp or buzz-like sounds (Jahn & Tuero, 2013). There is little information available on if Tyrannus savana make predator warning calls. The other source of communication is through body noises. It has been noted that in flight and if one can closely hear, the flapping wings of a Tyrannus savana in flight make a whistle-like sound possibly to communicate with other Tyrannus savana or other conspecifics that they are on the move (Jahn & Tuero, 2013). During courtship rituals the male Tyrannus savana wings making a rattling sounds communicating to females that they are available to mate (Jahn & Tuero, 2013).

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

The Tyrannus savana has an omnivorous diet of feeding off of both animal tissues and fruits. For the most part and especially during the summer and breeding seasons the Tyrannus savana are known as insectivores and they primarily feed off of insects (Teul et al., 2007). The types of insects the Tyrannus savana consume are mainly flying arthropods like wasps, beetles or some flying termites (Jahn & Tuero, 2013). During the non-breeding season or when insects are very scare the Tyrannus savana makes a switch to a herbivorous diet where they will consume fruit like berries (Jahn & Tuero, 2013).

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
• herbivore herbivore
  • frugivore frugivore
• omnivore omnivore

• Animal Foods
• insects

• Plant Foods
• fruit

Predation

The only known predators of the Tyrannus savana are other conspecific birds that are mainly nest predators. The Glaucidium brasilianu is the only known bird predator to kill adult Tyrannus savana however, it is unknown if the Glaucidium brasilianu consumes the dead Tyrannus savana tissues (Motta-Junior, 2007). Nest predation of Tyrannus savana consists of many bird predators. This is the list of the known documented predators: Guira guira , Milvago chimango , Rupornis magnirostris , Caracara plancus , Ramphastos toco , and Falco sparverius theses predators are known to prefer to feed off of broods with more than one egg (Jahn et al., 2014). However, there is little available information for how these predators strike a nest, as adult female Tyrannus savana are known to provide the most parental care before and after hatching. There has been one documented case that has been done on the species Molothrus bonariensi which is known to successfully parasitize nests of tyrant flycatchers. This study proved that most Tyrannus savana nests are easily parasitized by the Molothrus bonariensi however, some Tyrannus savana have been found to reject the Molothrus bonariensi eggs after approximately four days. The Tyrannus savana would reject these eggs by pushing the Molothrus bonariensi eggs out of the nest to fall to their early deaths forcing the Molothrus bonariensi to breed again and find a new tyrant flycatcher to parasitize (Cavalcanti & Pimentel, 1988). There is little available information on Tyrannus savana anti-predator adaptations.

Ecosystem Roles

There is little available information on the ways that the Tyrannus savana impact their ecosystems. However, in its closely related species the Tyrannus tyrannus is known for helping control populations of insects during its breeding season and also helps disperse fruit seeds (Murphy, M., 1996). It can be assumed since Tyrannus savana consume similar things, Tyrannus savana is also likely helping out their ecosystems by their behavioral feeding habits. Both Tyrannus tyrannus and Tyrannus savana are known to mutually forage in flocks with one another (Jahn & Tuero, 2013). The only species that is known to have some success on parasitizing the Tyrannus savana is the Molothrus bonariensi which only parasitizes the nests where it adds its own eggs into nests of its hosts by forcing the Tyrannus savana to care for the Molothrus bonariensi eggs and neglect their own eggs (Cavalcanti & Pimentel, 1988).

Economic Importance for Humans: Positive

There is little available information on how Tyrannus savana helps people benefit. The only positive benefit it provides is that like its close relative the Tyrannus tyrannus since it is primarily an insectivore it helps control pest populations (Murphy, M., 1996).

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

There is little available information on how Tyrannus savana have ways that might be a problem for humans. There is also little information on members of the Tyrannidae family may be a problem for humans. It is possible that Tyrannus savana may attack humans they perceive as a threat near their nests.

Conservation Status

The only available information on the Conservation Status of the Tyrannus savana species was from the IUCN red list, listing the species as a lower risk for least concern since 2012. There is also little available information on the Conservation Status of Tyrannus savana subspecies. The only known impact that humans have on the Tyrannus savana is that for some Tyrannus savana that nest higher up in trees keep having their nesting habitats being altered by humans forcing them to migrate and nest in new areas closer to the ground (Jahn & Tuero, 2013). Little to nothing is being done to help this species.

Other Comments

1. The Tyrannus savana is one of the rare neotropical native bird species from South America that is known to have some individuals that vagrantly migrate as far as southern Canada ("Fork-tail Flycatcher," 2013).
2. French ornithologist Louis Jean Pierre Vieillot was the first person to describe the Tyrannus savana bird ("Fork-tail Flycatcher," 2013).

Additional Links

Encyclopedia of Life

Contributors

Taylor Schirmer (author), University of Wisconsin - Stevens Point, Christopher Yahnke (editor), University of Wisconsin-Stevens Point, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Cavalcanti, R., T. Martins Pimentel. 1988. Shiny Cowbird parasitism in central Brazil. The Condor , none found: 40-43. Accessed May 01, 2016 at http://www.jstor.org/stable/1368430?seq=4#page_scan_tab_contents .

Jahn, A., D. Tuero, A. Mamani, V. Bejarano, D. Masson, E. Aguilar. 2014. Drivers of clutch-size in Fork-tailed Flycatchers (Tyrannus savana) at temperate and tropical latitudes in South America. Emu , 114/4: 337-342. Accessed May 01, 2016 at http://www.publish.csiro.au/?paper=MU13084 .

Jahn, A., D. Tuero. 2013. "Tyrannus savana" (On-line). The Cornell lab of Ornithology Neotropical Birds. Accessed May 01, 2016 at http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=482636 .

Lehmen, P. 2009. "Fork-tailed Flycatcher - BirdFellow Social Field Guide" (On-line). Bird Fellow. Accessed March 17, 2016 at http://www.birdfellow.com/birds/fork-tailed-flycatcher-tyrannus-savana .

McCaskie, G., M. Patten. 1994. Status of the Fork-tailed flycatcher (Tyrannus savana) in the United States and Canada. Western Birds , 25/3: 113-120. Accessed May 01, 2016 at http://www.birdpop.org/docs/pubs/Pyle_et_al_2011_35th_Report_of_the_CA_Bird_Records_Committee.pdf .

McKitrick, M. 1990. Genetic evidence for multiple parentage in eastern kingbirds (Tyrannus tyrannus). Behavioral Ecology and Sociobiology , 26/4: 149-155. Accessed April 30, 2016 at http://www.jstor.org/stable/4600388?seq=1#page_scan_tab_contents. .

Motta-Junior, J. 2007. Ferruginous Pygmy-owl (Glaucidium brasilianum) predation on a mobbing Fork-tailed Flycatcher (Tyrannus savana) in south-east Brazil. Biota Neotropica , 7/2: 0-0. Accessed March 17, 2016 at http://www.scielo.br/scielo.php?pid=S1676-06032007000200038&script=sci_arttext&tlng=en.. .

Murphy, M. 1996. "Eastern Kingbird (Tyrannus tyrannus)" (On-line). Accessed April 30, 2016 at http://bna.birds.cornell.edu/bna/species/253/articles/introduction .

Regosin, J., S. Pruett-Jones. 1995. Aspects of breeding biology and social organization in the Scissor-tailed Flycatcher. The Condor , none found: 154-164. Accessed April 30, 2016 at http://www.jstor.org/stable/1368993?seq=1#page_scan_tab_contents .

Teul, M., V. Piaskowski, K. Williams. 2007. The breeding biology of the Fork-tailed Flycatcher (Tyrannus savana) in lowland pine savanna habitats in Belize. Ornitologia Neotropical , 18: 47-59. Accessed May 01, 2016 at https://www.zoosociety.org/pdf/BWBPubs/Teul2007.pdf .

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2008. "Fork-tailed Flycatcher" (On-line). WorldBirds. Accessed April 30, 2016 at http://worldbirds.eu/abcf/forktailed_flycatcher.htm .

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