Like the other members of its genus, the medium ground finch is strongly sexually dimorphic; the female's plumage is brown and streaky,[2] while the male's is solid black, with white tips to the undertail coverts.

With these changes in the environment, medium ground finches with short/stubby beaks adapted due to the seeds and food preferences.

[10] The speed of how medium ground finches have been able to change beaks' sizes and shape may be centered around epigenetics.

A research team led by Ms. McNew on the Galápagos Islands has measured the physical traits of wild birds and the genetics and epigenetics of two Darwin's finch species living at El Garrapatero, a rural area.

Some of the earlier studies showed that only one female out of 300 medium ground finches that were marked and used in the research relocated between both sites.

In the finches studied, epigenetic alterations between the populations were dramatic, but minimal genetic changes were observed.

[10] The evidence showed that in medium and small ground finches, most of the epigenetic mutations were related to beak size and shape.

[12] Evidence of evolution through character displacement has been found in a population of medium ground finches on the Galápagos island of Daphne Major.

[16] Medium ground finches make dome shaped nests, mainly in Opuntia cacti.

[19] The HMGA2 gene locus is responsible for the evolution of beak size and plays an important role in natural selection.

[21] Nests in urban areas are built using artificial materials, such as plastic, fishing lines, paper, and human hair.

[8] Urban areas provide more reproductive success, however medium ground finches suffer by the usage of human-related debris in their nests.

[8] 97% of the Galápagos Islands are protected national parks, however the increasing population causes more dense urban areas.

[22] The islands are easily affected by anthropogenic changes, and urban development has a large impact on the environment, ecology, and evolution of the native species.

[23] The medium ground finch feeds primarily on seeds, although it is also known to eat flowers, buds, and young leaves, and the occasional insect.

[24] Scientists have found that due to urbanization, medium ground finches are showing changes in the size and shape of their beaks.

Medium ground finches eat the seeds of Tribulus cistoides, a low lying flowering plant.

[21] Scientists found that there was a 1.25% increase on feeding on T. cistoides seeds in more urbanized towns rather than natural habitats.

[21] This suggests that medium ground finches located in towns or urbanized areas have a stronger preference for small mericarps than do those living in natural habitats.

[8] This is how natural selection can occur: the birds' environment can influence the success of offspring and can possibly bring about evolution of finches in urban areas.

Even though finches in urban areas have higher reproductive success, they still exhibit mortality due to human pollutants such as plastic being trapped in nests.

Due to climate change, El Niño and La Niña are expected to occur more frequently.

[18] In a La Niña year, low precipitation results in the scarcity of food for finches, causing low reproductive success, while higher precipitation during El Niño years leads to an abundance of food, which can enhance breeding success,[8] allowing finches to produce up to twice as many eggs.

In 1977, the drought caused a decrease in medium ground finches with smaller beak size living because of the rare small seeds available.

It was the Grants that observed beak size had increased by 4% because only finches that knew how to eat larger seeds were able to survive and reproduce.

[30] With the climate changes occurring, medium ground finches would be able to survive because of their ability to adapt with droughts or heavy rain.

The medium ground finch has been under parasitism of the fly Philornis downsi[27] as well as the avian pox virus (Poxvirus avium).

[27] Using a new mathematical model, a 2015 study[27] suggested the population of 270,000 birds on Santa Cruz may become extinct in 50 years.

In the Galápagos Islands there has been no indication of bird extinctions, however, this may become a possibility as more people begin to inhabit and visit the area, introducing parasites.

[27] Possible solutions include the introduction of parasitic wasps which would lay eggs on the larva, or cotton wool treated with a pesticide which the adult birds would use when constructing the nest.