Some Results from the Monitoring Program
Hummingbird Diversity Patterns:
HMN sites are divided into geographic classes defined by latitude, longitude, and elevation. The following graphs show average values for estimated abundance and hummingbird richness (the number of hummingbird species) per monitoring session for all sites within a geographic class. See Sites for more information about geographic class.
ESTIMATED ABUNDANCE OF HUMMINGBIRDS PER MONITORING SESSION: HMN’s estimated abundance of hummingbirds at each site provides the information needed to estimate population sizes and thus to detect trends in hummingbird populations. Indian Peak, the only central Californiat site has significantly more hummingbirds per monitoring session than any other site in the Network.
2005 only
2002-2004
AVERAGE NUMBER OF HUMMINGBIRD SPECIES PER MONITORING SESSION: Perhaps the most unexpected result is that the southeastern Arizona sites are divided into two longitudinal classes which correspond with the Sonoran and Chihuahuan desert vegetation boundaries.
Is it an intriguing coincidence or does this result reflect a larger biogeographical pattern? Results, such as these, show that to understand hummingbird populations, we need to monitor them throughout their range.
2005 only
2002-2004
BREEDING Results
EXTENDED BREEDING RANGE OF VIOLET-CROWNED Hummingbird - We discovered Violet-crowned Hummingbirds breeding fifty miles farther north than previously known.
BLACK-CHINNED HUMMINGBIRD -
A few females enter our traps just before egg-laying and then return about 1.5 to 2 hours later after egg-laying. The following table shows most lost 0.5g.
Date of capture of gravid |
Weight |
Time between captures |
Age of female |
|
|
before egg-laying |
after egg-laying |
|
|
6/14/03 |
3.9 |
3.4 |
2 hours |
|
6/12/04 |
4.3 |
3.8 |
1 hr 36 min |
at least 6 years old – originally banded on 6/26/99 as an adult |
4/30/05 |
3.9 |
3.4 |
|
|
5/30/05 |
3.9 |
? |
1 hr, 6 min |
|
AGES of oldest and youngest nesting females. To our knowledge, the capture of a hatch year Costa's with an egg in California is the first evidence that hatch year hummingbirds are capable of breeding
Hummingbird Species |
Age of oldest nesting female |
Age of youngest nesting female |
Black-chinned |
6 years |
1 year |
Costa’s |
8 years |
Hatch year |
Anna’s |
5 years |
1 year |
Broad-billed |
7 years |
1 year |
MIGRATION Results
We did not detect any Rufous migration through California and Arizona in 2005. The number of Rufous breeding at the British Columbia sites was less and more variable in 2005 than in 2004. The lack of Rufous at the southern latitude sites during migration is an unusual event and potentially problematic. See HMN's Rufous Monitoring Project.
FIGURE OF RUFOUS HUMMINGBIRD OCCURRENCE PATTERNS AT HMN SITES, 2004-2005. Rufous migration was almost non-existent at both California and Arizona sites in 2005.
LONG-DISTANCE RECAPTURES are exciting for they give tangible proof that these incredibly small birds travel long distances. These recaptures are rare events, but the HMN has been fortunate to be involved with the ones below. We also have a number of birds moving between sites within states. The colored lines represent the travel of individual hummingbirds between the locations at the end of each line. The colored dots are HMN monitoring sites. The lines that end without a dot indicate that the bird was either banded or captured by someone other than an HMN scientist. The line at the lower right (ending with LA) indicates a bird banded in Arizona that was recaptured in Louisiana.
