USGS

Patuxent Wildlife Research Center

whiteshadow

LA cranes taken by Greg Smith

Telemetry Effect on Copulation and Incubation Constancy

Prepared by Glenn H. Olsen, USGS Patuxent Wildlife Research Center

 

The Whooping Crane Eastern Partnership (WCEP) has been releasing whooping cranes (Grus americana) since 2001 with the goal of establishing a reintroduced population in eastern North America. To date the effort has resulted in the release of more than 200 whooping cranes into the wild. The population follows a migratory path from central Wisconsin to wintering sites in Florida and other southern states. While survival is good, the whooping cranes do not demonstrate adequate reproductive success. There is some anecdotal evidence that the leg band mounted radio transmitters used to track cranes may be interfering with copulation (thus reducing egg fertility) and nesting behavior. For example, in 2 cases, the breaking of a bird’s antenna was associated with a change from laying infertile to fertile eggs 

 

Transmitters, either with an intact antenna or a shortened antenna, may cause discomfort during incubation, which may lead to increased nest abandonment. Nest abandonment has been observed frequently in this population, compared to the Aransas-Wood Buffalo population. Leg band transmitters have been used in the Aransas-Wood Buffalo population in the past, but never at levels above 2-3% of the population, and primarily in juvenile birds.

 

During 2013, 8 pairs of sandhill cranes in the captive colony at USGS Patuxent Wildlife Research Center were selected for a study of transmitter effects on egg fertility and incubation. In each year, 4 pairs received leg band mounted dummy transmitters complete with antennas, while 4 control pairs did not receive transmitters. During the winter of 2013-2014, treatment and control roles were switched. The results from 2014 are reported in Table 1. Eventually we will also examine differences between the two years.

 

In April, 2014, the male in one pair (S9-10) was discovered to have a fractured humerus. This required surgery to repair, plus a sling for much of the breeding season. This pair produced no fertile eggs this season and may have to be removed from the study.

 

Table 1. Results from 2014 monitoring of sandhill cranes fitted with transmitters, and control birds, in terms of egg fertility.

 

Treatment

Pen ID

Fertile Eggs

Infertile Eggs

Unknown

% Fertile

Control

R23/24

4

0

0

100

Control

R29/30

2

1

1

50

Control

Y41/42

4

2

0

67

Control

S1/2

4

0

0

100

  Control Subtotal

 

14

3

1

82

Transmitter

R9/10

1

5

0

17

Transmitter

R31/32

0

4

0

0

Transmitter

S17/18

3

1

0

75

Transmitter

S9/10

0

1

1

0

  Treatment Subtotal

 

4

11

1

27

 

 

In 2013 there appeared to be no effect of the transmitters on fertility (data not reported here), with the fertility rate for the transmitter-equipped birds being higher than the controls. The opposite was true this year, with the transmitter equipped birds having a lower fertility rate, 31% versus 78% for the controls. We still need to do the analysis by pairs.

 

In addition to looking at transmitter effects on fertility, we looked at the effects on incubation by placing a data logger egg in 7 of the nests this year to replace one egg. The cranes were then allowed to incubate to term. The analysis of this data is just starting, but no cranes abandoned their nests during incubation.

 

Now we are watching for winter effects of transmitters on the birds, such as ice build-up or problems tucking legs up into the feathers. We will continue making observations this winter on the birds with transmitters.

 

We thank Barbara Clauss and Brian Clauss, lead biological technicians and the entire USGS Patuxent Wildlife Research Center crane crew for their help in this study.



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