DOI: 10.5061/dryad.sn02v6xfj
title: Population and nesting habitat survey for Oreotrochilus chimborazo chimborazo

description: The adaptive significance of group-living has promoted considerable debate
 about the potential role of environmental drivers in the evolution of
 coloniality. Nest aggregations may result as a plastic response of
 reproductive individuals to limited substrate availability and favorable
 environmental conditions for nesting (Limited Substrate Availability
 Hypothesis). However, few studies have demonstrated the direct role of
 environmental factors in promoting social aggregations. A population
 survey of Oreotrochilus chimborazo chimborazo (Chimborazo Hillstar), a
 hummingbird subspecies endemic to the Ecuadorian High Andes, resulted in
 the identification of 7 nesting aggregations and 13 solitary nests. Of a
 total of 74 active nests detected, most (82%) were found in reproductive
 colonies. Furthermore, nesting aggregations were consistently associated
 year-round with roosting groups of males and non-reproductive females, a
 unique case among birds. These findings challenge the widespread
 assumption that hummingbirds are highly competitive solitary nesters. The
 subsequent characterization of Chimborazo Hillstar nesting habitat
 revealed that wind speed, temperature, humidity, and landscape features
 associated with substrate availability, ground cover vegetation, and water
 represent environmental factors associated with nesting, consistent with
 the Limited Substrate Availability Hypothesis. However, a semi-natural
 “experiment” comparing occupancy of solitary nesting locations versus
 nesting aggregations revealed that only 45.5% of the sites available for
 solitary nesting showed individual active nests, significantly lower than
 the 95% expected by random simulations. In contrast, nesting aggregations
 consistently had multiple active nests at significantly higher frequencies
 than expected, producing broods across multiple reproductive seasons.
 These results suggest that other factors beyond those associated with the
 Limited Substrate Availability Hypothesis may play a role in the
 development of nesting/roosting aggregations in the Chimborazo Hillstar,
 emphasizing the importance of the interaction of environmental and social
 factors in driving coloniality in birds.
description: # Population and nesting habitat survey for *Oreotrochilus chimborazo
 chimborazo* [Access this dataset on
 Dryad](https://doi.org/10.5061/dryad.sn02v6xfj) \- This dataset is
 associated with the following Dryad files: Dryad_Raw_Data.docx and
 README_Dryad.md Dataset associated with Cañas-Valle and Bouzat (2024)
 publication in *Ornithology* (Vol 142: 1-13), entitled "Ecological
 drivers of coloniality in *Oreotrochilus chimborazo chimborazo*
 (Chimborazo Hillstar), a hummingbird endemic to the High Andes of
 Ecuador." See Materials and Methods section of Cañas-Valle and Bouzat
 (2024) for specific descriptions of methods used for the collection of the
 data reported here.
 [https://doi.org/10.1093/ornithology/ukae063](https://doi.org/10.1093/ornithology/ukae063) ## Descriptions **Raw Data associated with the study published in** ***Ornithology*** **(2024)** 1. Population survey raw data 2. Nesting survey data 3. Nesting and roosting survey of colonial aggregations 4. Avian checklists 5. Characterization of Chimborazo Hillstar habitat 1. Quantitative variables associated with ravines as potential habitat for *O. c. chimborazo* 2. Landscape survey of qualitative variables associated with *O. c. chimborazo* habitat 6. Data on semi-natural experiment comparing solitary vs aggregated nesting sites 1. Occupancy and Recurrency of “experimental” culverts for solitary nesting and nesting aggregations 2. Simulations for random assignment of individuals to solitarily and aggregated nesting sites ### **Population Survey Raw Data** * *Sampling Transects*: Identifiers of sampling transects * *Individuals (N)*: Number of active individuals detected at sampling transect * *Replicates (rep)*: Number of sampling replicates at sampling transect * *N/rep*: Number of individuals detected per sampling replicate at a transect * *Area (hectares)*: Sampling area surveyed (in hectares) * *Density (N/hectare)*: Density estimates of area sampled at individual transect (expressed as number of individuals per area in hectares) ### **Nesting Survey Raw Data** * *Nest Aggregations, Solirtary Nests; Locations with No-Nests*: Number of Localities (N) with Nest Aggregations, Solitary Nests and No-Nests. * *Location ID*: Identifiers of nesting localities * *Nests*: Number of nests detected at a locality ### **Nesting and Roosting Survey of Colonial Aggregations** * *Sampling Seasons*: Sampling seasons for surveys of nesting aggregations * *Nesting Sites Location ID*: Identifiers of Locations of Nesting Sites * *All Nests*: Number of Total Nests detected at nesting locations * *Active Nests*: Number of Active Nests detected at nesting locations * *Roost M/F*: Number of Roosting Males (M) and Females (F) detected at nesting locations ### **Avian Checklists** * *Common name*: Common Species Name * *Species*: Current scientific name of species * *T1; T2; RT1; RT2; RT3; RT4; RT5*: Identifiers of sampling transects * *X*: Represent check for detection of a species at a spceific sampling ttransect ### **Characterization of Chimborazo Hillstar Habitat** #### **Quantitative Variables associated with Ravines as Potential Habitat for** ***O. c. chimborazo*** * *RAVINE*: Ravine Transect Identifier (RT1-RT5) * *-0m; -500m; 1000.; 1500m; 2000m*: Sampling site at a Ravine Transect for measuring microhabitat conditions inside (IN) and outside (OUT) of ravine * *Day*: Day at which sampling variables were measured (Day 1; Day 2) * *Hour*: Time at which sampling variables were measured at a specific sampling site * *IN/OUT*: Location (IN: Inside Ravine; OUT: Outside Ravine) where quantitative variables of microhabitat conditions were measured * *Wind*: Quantitative variable associated with wind speed (measured in km/h) * *Temp*: Quantitative variable associated with temperature (measured in centigrades (C)) * *Humid*: Quantitative variable associated with humidity (measured as percent of humidity (%)) #### **Landscape Survey of Qualitative Variables associated with** ***O. c. chimborazo*** **Habitat** * *Location ID*: Identifier of sampling location * *Nesting*: Nesting variable refers to location with no nests (Nest-n), solitary nests (Nest-1), and aggregated nests (Nest-mny) * *Water*: Ecological variable associated with water availability (Wat-y: water presence; Wat-n: no water) * *Cover*: Ecological variable associated with vegetation cover (Cov-y: vegetation cover; Cov-n: no cover) * *Alpines*: Ecological variable associated with the presence of Alpine flowers (Alp-y: Presence; Alp-n: Absence) * *Chuquiragua*: Presence (Chu-y)/Absence (Chu-n) of Chuquiragua Jussieui * *Surface*: Presence (Sur-y)/Absence (Sur-n) of solid surface as nesting substrate * *Grazing*: Presence (Gra-y)/Absence (Gra-n) of grazing animals (sheep, lamas, or vicunas) * *Trash*: Human Disturbance as indicated by evidence of human activity (Tra-Y: Human disturbance; Tra-n: no evidence of disturbance) ### **Data on Semi-Natural Experiment comparing Solitary vs Aggregated Nesting Sites**_Data #### **Occupancy and Recurrency of “experimental” culverts for solitary nesting and nesting aggregations** * *Experimental Culverts*: Experimental culverts for solitary nesting * *Nesting Aggregations*: Localities for nesting aggregations * *Nesting*: * *Nests*: Number of nests detected at Experimental Culverts and Nesting Aggregations * *Occupancy*: Occupancy describes sites without signs of nesting (empty), with either remnants of nests or fecal splats (signs), with old nests not firmily attached or without fresh feces (old), and nests with a brooding female or fresh feces (active). * *Feces*: Categories of relative use of nesting sites based on relative thickness of fecal splats (see Methods in Cañas-Valle and Bouzat 2024) * *Recurrency*: Signs of current (Yes) or historic (Historic) reuse of localities for nesting. * *Roosting (Male; Female)*: Number of roosting Males and Females detected at Experimental Culverts and Nesting Aggregations #### **Simulations for Random Assignment of individuals to Solitarily and Aggregated Nesting Sites** * *Solitary*: Solitary nesting locations * *Colonial*: Colonial nesting locations * *Available Nesting Sites*: Number of available nesting sites at Solitary and Colonial nesting locations * *Observed Active Nesting*: Observed number of Active Nests at Solitary and Colonial nesting locations * *Expected Nesting*: Expected number of Active Nesting sites at Solitary and Colonial nesting locations based on the random assignment of individuals observed at Solitary and Colonial nesting locations (based on simulations with 1500 replications) ## Sharing/Access information This dataset is associated with the following Dryad files: Dryad_Raw_Data.docx and README.md The dataset presented here is associated with the study by Cañas-Valle, G.X. and J.L. Bouzat (2024), published in *Ornithology* (*Ornithology*, Volume 142, Issue 2, 1 April 2025, ukae063, [https://doi.org/10.1093/ornithology/ukae063](https://doi.org/10.1093/ornithology/ukae063)) Cañas-Valle, G.X. and J.L. Bouzat. 2024. Ecological drivers of coloniality in the Chimborazo Hillstar, *Oreotrochilus chimborazo chimborazo*, a hummingbird endemic to the High Andes of Ecuador. *Ornithology* 142(2): 1-13.