A study published in Science on January 11 seems to be the first to lay empirical evidence that concur with Charles Darwin’s hypothesis: … that mate selection might have contributed to the evolution of intelligence or cognitive abilities. Scientists from China and the Netherlands collaborated in a study on budgerigars, Melopsittacus undulatus. Based on what they observed, problem-solving skills apparently increased the attractiveness of male birds. Accordingly, female birds chose to spend more time with male birds that appear to be smarter.
Darwin on mate selection
In animal kingdom, mate selection is a real deal. One of the generalized traits that distinguish the animal from the plant is the former’s tendency to select a mate. Animals, including humans, have their set of preferences when it comes to choosing a mate. While plants chiefly let nature do the “selection” for them, animals tend to seek a potential mate by themselves. And when they find a suitable mate of their choice, they often make a conscientious effort to succeed at coupling. In particular, males engage first in a courtship ritual, for example, by wooing a female with a song, a dance, or by a display of beauty or prowess.
Sexual selection evolved as one of the means of natural selection. A male, for instance, chooses a female to mate with, and, if need be, may tenaciously compete against other males to stack the odds in his favor. Charles Darwin’s long-standing theories on sexual selection are still relevant to this day. Darwin believed that sexual selection had a key role in how humans evolved and diverged into distinct human populations. In view of that, sexual selection could have contributed as to how intelligence evolved.
Intelligent males, more attractive
Many studies on birds revolved around the notion that female birds favor male birds with vibrant feathers or stylish songs. A recent study claims that intelligence is preferred over such fancy features and skills.
In the first experiment conducted by Chen and colleagues, small budgerigars (Australian parrots) were observed inside their cages to test the hypothesis that intelligence might affect mate selection. To do that, they allowed each female budgerigars to choose among a pair of similarly-looking male budgerigars to interact with. The chosen males were called preferred whereas those that were not were referred to as the less-preferred. Next, they trained the less-preferred males into learning a skill that opens closed lids or boxes. They, then, allowed the female budgerigar to observe the less-preferred male demonstrate the skill. Consequently, almost all of the females changed their preference. They chose the less-preferred males over the initially preferred males.
To test if this preference was social rather than sexual, they conducted a second experiment with a similar experimental design but this time a female budgerigar was exposed to two females (instead of males). The results showed that none of the female budgerigars changed their preferences. [1, 3] Based on these experiments, the researchers concluded that the demonstration of cognitive skills altered mate preference but not necessarily social preference.
Video of the animal model, male budgerigar that learned a problem-solving skill that seemingly increased its attractiveness to females. [Credit: Hedwig Pöllöläinen].
Why did mate selection evolved? The answer could be associated with the species survival or longevity. Individuals must be able to stay in the mate selection pool, if not on top of it. In general, males deemed as superior or “preferred” will gain higher chances at mating, and thereby will have better opportunities at transmitting their genes as they dominate the access to fertile females. Females, on the other hand, gain an upper hand from the mate selection by being able to choose the seemingly finest among the rest. Females must choose. That is because they have a generally limited reproductive opportunity to give life to. Moreover, the energy that a female invests in producing an offspring is so great that it has to be worth it.
— written by Maria Victoria Gonzaga
1 Chen, J., Zou, Y., Sun, Y.-H., & ten Cate, C. (2019). Problem-solving males become more attractive to female budgerigars. Science, 363(6423), 166–167. https://doi.org/10.1126/science.aau8181
2 Jones, A. G., & Ratterman, N. L. (2009). Mate choice and sexual selection: What have we learned since Darwin? Proceedings of the National Academy of Sciences, 106(Supplement_1), 10001–10008. https://doi.org/10.1073/pnas.0901129106
3 GrrlScientist. (2019, January 11). Problem-Solving Budgies Make More Attractive Mates. Forbes. Retrieved from https://www.forbes.com/sites/grrlscientist/2019/01/10/problem-solving-budgies-make-more-attractive-mates/#515f24d66407
Blacked-legged Kittiwakes are pelagic gulls that often feed on fish and macro-zooplankton at the ocean surface. They breed in colonies ranging from few to thousands of pairs which prominently observed in their open, sea-cliff nesting habitats. Blacked-legged Kittiwakes are the most popular models for research because they can be easily monitored and captured. They also considered as prime indicators of fluctuating conditions in marine ecosystem. The purpose of this research is to collect live sperm of blacked-legged Kittiwakes using a non-invasive method. Also, be able to provide information on suitable extenders and timing in relations to the breeding phenology. Additionally, it will offer informations to different disciplines including veterinary science, conservation biology, ecotoxicology and evolutionary biology.
Sperm collection of Blacked-legged Kittiwakes
Sperm of blacked-legged Kittiwakes were obtained by firmly massaging the lower back and the tail base of the male bird. Since, the researchers observed that during mating the male tend to wag their tails thus, releasing the sperm naturally. After massaging the handler lift the tail, clear the feathers around cloaca and gently squeeze the cloacal area. While doing this a capillary tube placed on the top of the cloaca to collect directly the translucent liquid. Then, verified directly to the laboratory under the microscope.
The result demonstrates a successful collection of live sperm under field condition of blacked-legged Kittiwakes for the first time. In which the researchers discovered two extenders suitable for maintaining the sperm however, undiluted sperm also performed well in terms of survival. Since, seminal fluids alone are sufficient enough to maintain the sperm alive. Though, the researchers still recommend using sperm extenders since it is necessary to dilute highly concentrated ejaculates. Also, extenders are necessary on sperm quality examination when comparing experimental groups and sperm production.
Blacked-legged Kittiwakes are strictly monogamous and stores semen inside their body unlike passerine birds that stores semen in seminal glomera. Interestingly, one has to keep in mind that sperm quality may vary seasonally. So, the researchers suggest that one should statistically account for this effects using date relative to laying eggs. Also the researchers recommends to target specific time window when the birds are about to copulate but not after copulation within a day.
Source: Prepared by Joan Tura from BMC Avian Research
Volume 9:24, 14 July 2018
Eastern whip-poor-will (Antrostomus vociferous) is continuously declining due to habitat loss and unavailability of insects for food. Little is known about whip-poor-will migration because of their nocturnal quite habit during non-breeding season. At high latitude 80% avian species are migratory wherein factors affecting migration includes predators, anthropogenic threats and pathogens. Migratory strategies allows individual to track seasonal changes mostly for temperate breeding aerial insectivores. However, population declines among temperate insectivore birds due to extreme weather condition, cost of migration and reliance on sensitive prey. In addition it is important to determine the migratory routes, year round habitat requirement and temporal constraints of threatened species.
Geolocator deployment of Whip-poor will
There were 20 males and 2 females of whip-poor-will have been tracked using geolocators in four regions of Canada. The study shows that this species breed more in northern part than southern breeding population and experienced different wintering conditions. Also a high migratory cost happens such as novel threats, energy expenditure and the ability to adjust time in tracking breeding ground condition. In contrast, both eastern and western breeding individuals wintered together wherein mostly concentrated in Guatemala and some provinces of Mexico. However, male often have higher benefits of early arrival on the breeding grounds thus accept higher cost of wintering further. Additionally, early arrival on breeding grounds is more advantageous on whip-poor-will males allowing occupation on higher quality territories.
On the other hand female whip-poor-will forced to migrate further on lower latitude with less competition and more abundant resources. Most of this species travel overland through Mexico and Central America. However, only two individuals flights across portion of the Gulf of Mexico during autumn and spring. It just shows that this pattern is the response to prevailing winds and availability of resources along different route. Also more species migrating along Eastern North America, South and Central America over ocean flights during autumn. While in spring more species taking longer over land route around western side of the Gulf of Mexico.
Therefore, geolocators is helpful in identifying wintering areas, stopovers and migratory route of whip-poor-will. These migratory stopovers in the southeastern and central United States as well as in southern Mexico and Central America are both important for the whip-poor-will species. Finally, habitat protection and insect population might increase the number of these species despite pressures of long migrations and climate changes.
Source: Prepared by Joan Tura from Springer BMC Zoology
Volume 2:5, 2017
Waterbirds are very important indicators in the ecosystem particularly wetlands. Due to climate change and human activities such as pollution, over-hunting and habitat loss about 23% globally are declining. Some have been listed as threatened species by the International Union for Conservation of Nature (IUCN) for about 19% worldwide. In view of this severe condition, waterbirds diversity has been rapidly decreasing and its conservation status received attention. In China there are 53.6 million hectares of wetlands making it the first among Asia and fourth in the world. There were different wetland types in China including swamps, rivers, lakes, coastal wetlands and estuaries. Conservation of waterbirds in China has been implemented establishing nature reserves, designating key habitat and captive breeding to increase population.
Population Trends of Waterbirds in China
According to Wetlands International there were 871 waterbird species in 32 families and 8 orders in the world. In China, 260 waterbird species has been identified that belongs to 21 families. 84 species exhibited a declining trend, 35 species remained stable while 16 species showed increasing trends. Threatened species includes Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern and Data Deficient. Moreover, the migratory and residents waterbirds suffered serious threats and a total of 38 species listed as threatened species. Also there were 6 species listed as Critically Endangered, 16 species Vulnerable, 16 species Endangered and 27 species as Near Threatened.
Threats to waterbirds include both direct and indirect human activities such as illegal hunting, disturbances, pollution and habitat loss. However, habitat loss is the most common threat because of large scale reclamation in both coastal and inland wetlands. According to the national surveys a decreased of 3.4 million hectares of wetlands wherein coastal losses more than inland wetlands. In recent years, continuous development and industrialization affects the natural habitats of waterbirds. In which foraging time have been reduced, vigilance behavior increased and recurrently being flushed away. As a consequence human disturbances forced the birds to abandon habitats and nest due to breeding failure.
Therefore, waterbirds in China might be in more serious situation than we thought that is why conservation must be implemented. Like restoration of degraded wetlands, public awareness, cracking down on illegal hunting and enforcement of Wildlife Protection Law. Additionally, restoration of highly threatened species through artificial intervention is needed. As well as promoting cooperation between international and regional information on conservation.
Source: Prepared by Joan Tura from Springer Nature BMC Avian Research
Published: 28 April 2018