Field Observation 3: Social Behavior and Phenology

On March 10, the first Sunday of spring break, I was in Puerto Rico. Specifically, the area around San Pablo Bayamon hospital was where I decided to observe birds. The time was 3:00 PM when I began. Chose this area because due to unforeseen circumstances I waited at the hospital for a couple hours and there just so happened to be an abundance of birds in the area. The weather was nice, warm, and sunny. The complete opposite of Vermont’s usual weather. The temperature was somewhere in the high 70's or low 80's.
For my observation I sat on a bench in front of the hospital and observed the behaviors of the birds that flew or walked in my line of sight. The most abundant species I noticed were Greater Antillean Grackles. In general, they were quite possibly the most abundant bird on the island with doves being a close second. Since they were everywhere and not very shy I chose this species to focus on.
Compared to the light brown with some streaks of white and dark brown plumage of the Zenaida Dove, the Greater Antillean Grackles has a solid black plumage with iridescence in the right lighting. The evolutionary advantage of having such dark plumage is probably to camouflage in the upper canopy. As this is a bird where when it is not in a an urban environment likes to perch up in the top understory. The Zenaida Dove I believe uses its plumage to camouflage with the ground, because despite it having the ability to fly I noticed they do a lot of foraging along the ground and usually on ground the same color as them. From an aerial view it would be difficult to pick out the doves. I assume that broad tailed hawks would prey on them given the chance and their plumage serves as a natural defense against predation.
The Greater Antillean Grackles showcased a variety of behaviors as I observed them. I witnessed foraging behavior as they flew from a nearby tree to the road in front of me to pick for any scraps or small insects. There was rainfall earlier that day, so there were some small puddles still present. Some of the grackle would fly to these puddles for a quick drink or soak. When they soaked they hopped into the puddle extending their wings somewhat, hopping out, and then shaking off to dry. When they weren’t on the road foraging, they were in the trees roosting. While in the trees, I witnessed small disputes between grackles as they fought over roosting spots. I noticed that before disputes happened one of the individuals involved would lower their head, extend their wings in a folded manner, and extend their tail feathers. I have observed them to do many things with the shape and direction of their tail feathers with or without other birds present, so I am not completely sure if it is for communication or something else. As far as what they’re trying to say if it is for communication, I think they might be communicating their mood. When they’re the most hostile or dominate they spread their tail feathers the widest. They also let out a call that sounds like a grackle, so I figure that’s how they received their name.
When I used the “psssh” method it attracted some grackles towards me. They flew over and walked around as if they were looking for something. When I stopped making a “psssh” sound they looked the most confused as if contemplating why did I come here in the first place. Based on what I saw them do when I used the “psssh” method, I believe it mimics a call to forage. When I did it the birds would generally not come directly towards me, but forage around me. I think this method works because it alerts smaller birds of local foraging opportunities. It is probably enticing because generally smaller birds make the sound, so if that sound is being made and I’m a small bird too or a slightly larger bird I can bully that bird for the food they found.

Posted by david4561 david4561, March 25, 2019 23:12

Observations

Photos / Sounds

What

Zenaida Dove Zenaida aurita

Observer

david4561

Date

March 10, 2019 02:20 PM ADT

Photos / Sounds

What

Greater Antillean Grackle Quiscalus niger

Observer

david4561

Date

March 10, 2019 05:31 PM ADT

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