Tiny birds are grouped together here for ease of identification. Most are not related to each other.

https://www.flickr.com/photos/stirwise/2450795738/sizes/m/
Author: stirwise (Kerry Lannert) Creative Commons Attribution-Noncommercial-No Derivative Works 2.0 Generic

• Small, energetic, acrobatic bird
• Relatively tame and bold; often seen at feeders, and usually investigates new feeders before other birds
• Scolding call is a "chick-a-dee-dee-dee"; song is a simple two notes
• Survives cold winter nights by going into torpor

https://dwrcdc.nr.utah.gov/rsgis2/search/Display.asp?FlNm=trogaedo
Author: Uknown.Utah Division of Wildlife Resources. Public Domain.

• Plain brown bird which cocks tail and can be surprisingly bold, especially when near nest
• Song is very loud and clear-ringing
• Eats insects and spiders
• Winters in Central and South America

https://commons.wikimedia.org/wiki/File:Poecile_gambeli2.jpg
Author: Jerry Friedman. GNU Free Documentation License, v.1.2; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts

• Similar to Black-capped Chickadee except for eye stripe
• Prefers higher elevations and coniferous trees, but can be seen in suburban Colorado Springs
• Song and call are similar to that of Black-capped, but song has more notes

https://www.flickr.com/photos/marklwatson/5970502627/
Author: Mark Watson. Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic

• Male Broad-tailed has red gorget (throat); female has plain throat and is less colorful overall
• Male makes a characteristic high-pitched buzz as it flies; more often heard than seen
• Individuals can go into torpor on cold nights

https://www.flickr.com/photos/pazzani/6267472947/
Author: Mike’s Birds. Creative Commons Attribution-ShareAlike 2.0 Generic

• Tiny, acrobatic bird, often seen around houses and CC campus.
• Flock movement is similar to a cloud of gnats travelling along lines of bushes or trees.
• Birds are rather tame. If you stand in the path of the flock, they may pass very near you.
• Female has yellow eyes
• Eats insects and spiders; also berries, seeds, and suet.

https://www.flickr.com/photos/puttefin/8652929371/
Author: Kelly Colgan Azar. Creative Commons Attribution-NoDerivs 2.0 Generic

• Pert, very energetic bird; often cocks tail
• Look for white eye ring and white edges on tail
• Call is a squeaky wheeze