PURPLE MARTIN

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Purple Martin
Copyright © 2005 Eric Secker

Conservation Concern: NONE

Population Trend: Decreasing
Credibility: Very Poor

The Purple Martin is an uncommon, but locally common breeder in the CW Region.  These often colonial birds historically nested in tree cavities, but many populations in our area are now largely dependant on man-made "martin houses".  Preferred habitat is usually open fields or open areas near water.  Data on this species is very limited, but nonetheless, shows a considerable estimated decrease of at least 10% annually.

Trend Level

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1997-2004 Trend
Point Count Data
1988-2004 Trend*
All Observation Types

*Data gathered using a assortment of sampling methods  - for casual inferences only
  Avg. Yearly
Rate of Change:

The vertical axis numbers represent an index of the population change.

Note that the scales may vary between graphs.

Avg. Yearly
Rate of Change*:
 
  -25%   -10%  
   
   

 

 

Technical Notes (1997-2004 Trend)

Sample Size (Indiv.): 6

Sample Size (Records): 4

 

AVG. YEARLY RATE OF CHANGE:
(including standard error)
-110 to 59

 GOODNESS OF FIT:
Chi-square: 4.58, df 4, p 0.3328
Likelihood Ratio: 4.05, df 4, p 0.3997
AIC: -3.95
NOTE: (model fits if p values are above 0.05)

Download Table of All Observations

 

 

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Copyright © 2005 Audubon - Chicago Region & Bird Conservation Network

 

 
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