Long tails no enough?

There is a considerable amount of sexual dimorphism in great-tailed grackles (Quiscalus mexicanus), a type of blackbird. Sexual dimorphism is the difference in form between individuals of different sex in the same species.

Male great-tailed grackles can grow up to about 43 cm, including a tail that is almost as long as the body, and are jet-black in colour with a violet-blue iridescent sheen to the feathers. Females, on the other hand, are significantly smaller at about 33 cm, and are mainly brownish-black, with a pale brown throat and belly.

Great-tailed Grackle (Quiscalus mexicanus), Male

Great-tailed Grackle (Quiscalus mexicanus), Male

Great-tailed Grackle (Quiscalus mexicanus), Female

Great-tailed Grackle (Quiscalus mexicanus), Female

Sexual dimorphism is mainly attributed to sexual selection. Longer tail length has always been associated with territory acquisition and social mate attraction, in combination with size.

There can also be another explanation to sexual selection. Larger males have the advantage in acquiring territories, and females preferred to settle on the territories of larger males, probably because larger males were able to acquire trees with the most desirable nest sites.

Larger males have the advantage in acquiring territories

Larger males have the advantage in acquiring territories

Recently, it came into question whether animals also use glossiness, where their hair or feathers reflect light like a mirror, to signal to the opposite sex.

In a recent study conducted by PhD researcher Mr Matthew Toomey and colleagues from Arizona State University, Tempe, US, birds were captured, with photographs taken of them and their tails measured before being released. The glossiness of the bird’s feathers in each photograph was calculated using a reflectance spectrophotometer and computer software.

According to Mr Toomey, it was found that male great-tailed grackles were significantly glossier than females. Another discovery was that males with the glossiest feathers also had the longest tails. One possibility arising from this study is that glossiness may play a role in visual signaling and glossier males may be more attractive and better competitors for mates.

Glossiness may play a role in visual signaling

Glossiness may play a role in visual signaling

Glossiness can be a potential step towards the evolution of iridescence where selection for glossiness can result in a refinement of the microstructure of a feather.

Long tails are no longer enough to attract mates? Further research will be required to prove this theory.


“Female birds find males with glossy feathers more sexy,” by Jody Bourton. BBC, 23 March 2010. URL: http://news.bbc.co.uk/earth/hi/earth_news/newsid_8577000/8577316.stm (accessed on 3 April 2010).

Kristine Johnson, Emily DuVal, Megan Kielt & Colin Hughes, 2000. Male mating strategies and the mating system of great-tailed grackles. Behavioural Ecology, 11(2): 132-141

William A. Searcy and Ken Yasukawa, 1981. Sexual Size Dimorphism and Survival of Male and Female Blackbirds (Icteridae). The Auk, 98(3): 457-465

William A. Searcy, 1979. Sexual Selection and Body Size in Male Red-Winged Blackbirds. Evolution, 33(2): 649-661

“2 of 2 Great-tailed Grackle (Quiscalus mexicanus), Male,” by Michael “Mike” L. Baird, mike at mikebaird.com. URL: http://www.flickr.com/photos/mikebaird/4495734086/in/photostream/ (accessed on 5 April 2010)

“Great-tailed Grackle (Female) (Quiscalus mexicanus),” by Mike Baird, BairdPhotos.com. URL: http://www.flickr.com/photos/mikebaird/339193969/ (accessed on 5 April 2010)

“Quiscalus mexicanus,” by Pablo Lèautaud. URL: http://www.flickr.com/photos/pleautaud/2662384817/ (accessed on 5 April 2010)

“Quiscalus mexicanus,” by Pablo Lèautaud. URL: http://www.flickr.com/photos/pleautaud/3217071624/ (accessed on 5 April 2010)

You are my one and only… OR ARE YOU?

Though Adelie penguins (Pygoscelis adeliae) are monogamous, the couple does not spend the winter together. In fact, the pair migrates separately and will only return to the rookery where they last mate during the breeding season (from November to February). The males will arrive at the breeding site prior to the females to build the nesting sites. Unless one of the partners fails to return, the couple will reunite every breeding season. The penguins are able to recognise its mate’s call or even, physical features.

For first time breeders, there are generally three distinct types of visual/auditory courtship displays. (Watch this – courtship of penguins)

  1. Ecstatic. The male penguins will swing their head, and flap their flippers. These actions show possession of a breeding site, to attract females, and to keep other male intruders away.
  2. Mutual. Once paired, both the male and female penguins will stretch their head and neck upward.
  3. Bowing (Figure 1). Bowing displays reduce aggression; strengthen bonds and recognition between partners.
Figure 1 (Source: http://www.coolantarctica.com/gallery2/birds_1000_pic0012.html)

Figure 1 (Source: http://www.coolantarctica.com/gallery2/birds_1000_pic0012.html)

Are Adelie penguins truly monogamous?

Research has found that both male and female Adelie penguins may have more than one breeding partner in its life (F. M. Hunter, G. D. Miller and L.S. Davis, 1995). In fact, about 21-30% of the female penguins were involved in mating with more than one male in a single breeding season, either through extra pair copulations (EPC’s) or mate-switching (Harshaw, 2005).

A female may copulate with multiple partners to enhance genetic quality or diversity of her offspring. The female penguin may also mate with numerous males to (1) ensure that her eggs are fertilised in the event of her partner being infertile, (2) gain potential partners in the future years should her partner leave her (F. M. Hunter, G. D. Miller and L.S. Davis, 1995).

In addition, it seems that the females engage in EPC’s so as to collect more stones or nesting materials to build a better nest. This will benefit the males in terms of living conditions as well. Furthermore, after the eggs have been laid, the males have the responsibility to incubate them. As such, the male is unable to leave the nest to protect its mate from engaging in EPC’s since an unguarded nest will invite predation.

While we decide whether the Adelie penguins are indeed monogamous, it is important to note that the survival of all species of penguins is greatly challenged by weather conditions and food availability. According to Dee Boersma, a University of Washington biology professor, the population of penguins in the Punta Tombo colony has reduced by more than 20% in the last 22 years (Science Daily, 2009). Some possible reasons for the decline are human activities such as oil pollution and overfishing. As such, it is crucial human amend their ways to save our declining ecosystem.


“Adelie Penguins”, by Keith Dreher, n.d. URL: http://www.keithdreher.com/adelie.html (accessed on 6 April 2010).

“Adelie Penguins”, by National Geographic, n.d. URL: http://animals.nationalgeographic.com/animals/birds/adelie-penguin/ (accessed on 6 April 2010)

“Adiele Penguins – courtship 10”, by Paul Ward, 2001. URL: http://www.coolantarctica.com/gallery2/birds_1000_pic0012.html (accessed on 6 April 2010)

“Adiele Penguins – courtship, mating and chick hatching”, by BBC Natural History Unit, n.d. URL: http://www.arkive.org/adelie-penguin/pygoscelis-adeliae/video-09b.html? (accessed on 5 April 2010)

“Mating System”, by Lauren Harshaw, 2005. URL: http://www.bio.davidson.edu/people/vecase/Behavior/Spring2005/Harshaw/MatSys.html (accessed on 5 April 2010).

“Penguins”, by Sea World, n.d. URL: http://www.seaworld.org/animal-info/info-books/penguin/reproduction.htm (accessed on 6 April 2010)

“Penguins Marching into Trouble”, by Science Daily, 13 February 2009. URL: http://www.sciencedaily.com/releases/2009/02/090212171936.htm (accessed on 6 April 2010)

“Penguin Parenting: Adelie penguins reunite for their annual breeding rituals”, by Michelle Alten, July-August 1997. URL: http://findarticles.com/p/articles/mi_m0FRO/is_n4_v130/ai_19634761/ (accessed on 5 April 2010)

F. M. Hunter, G. D. Miller and L. S. Davis, August 1995. Mate Switching and Copulation Behaviour in the Adelie Penguin. Behaviour, 132(9/10): 691-707

Animals – Earthquakes predictors

In year 1948, two days before Ashgabat earthquake, there was this guy who saw many reptiles appearing in large numbers. Upon witnessing that unusual scene, he immediately reported to the relevant department. However, no one took notice of him and the earthquake proceeded to claim much destruction in the area. Also in 1978, a few days before the Central Asian earthquake, lizards and snakes left the caves and the places where they hibernate in. These show us that the animals are more sensitive to earthquakes compared to human.

Animals will exhibit unusual reactions just before an earthquake strikes. Some studies have shown, the surface and the subsurface of the earth will undergo extraordinary physical and chemistry changes before the occurrence of the earthquake. The changes include differences in sound, temperature, vibration wave, electromagnetic wave, the water’s chemical composition and many other more. These will stimulate certain animals as their nerve sensory organs are more sensitive than humans and therefore they will react more instinctively. For example, the dog in the video can feel the vibration earlier than the people in the room. Erratic behavior in dogs, such as excessive barking or biting, could be used to forecast quakes (Maryann Mott, 2003).

Besides dogs, other mammals such as cats, mice, cattle will also have unusual behaviors. They will be frightened and start to running, or have cluster migration. A few of them may have different reactions such as being depressed and sluggish. Animal organisms are very sensitive to system and environment change. They are just like an seismograph, which can show us the signals of earthquake effectively. Animals does not only give love and happiness, they also protect us from major disasters that even a scientist cannot explain or predict. This is why we love them so much.

1. “Can Animals Sense Earthquakes?” by Maryann Mott, November 11 2003. URL: http://news.nationalgeographic.com/news/2003/11/1111_031111_earthquakeanimals.html (accessed on 3rd Apr 2010)

2. “Animals and Earthquakes,” by David Jay Brown. URL: http://animalsandearthquakes.com/index.htm (accessed on 3rd Apr 2010)

3. “The Use Of Animals In Earthquake Prediction,” by Dr. George P.C. URL: http://www.rense.com/general61/use.htm (accessed on 3rd Apr 2010)

4. “Earthquake Prediction by Animals: Evolution and Sensory Perception,” by Joseph L. Kirschvink, Bulletin of the Seismological Society of America, 90, 2, pp. 312–323, April 2000.

5. “My dog Sophie senses the 6.5 earthquake at the Times-Standard newspaper in Eureka CA,” by BrianWheeler12 YouTube Channel, January 10 2010. URL: http://www.youtube.com/watch?v=FV4EMzyJsqU (accessed on 4 Apr 2010).