Freitas and Francisco • REPRODUCTION OF THE YELLOWISH PIPIT 
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FIG. 1. Nest and eggs of Anthm lutescens (Motacillidae). 
populations of Meadow Pipits (A. pratensis) 
(Coulson 1956. Davies 1958). Incubation (laying 
to hatching of the last egg) and nestling periods 
(hatching to Hedging of the last young) were 
compared to England populations of Meadow 
Pipit. These analyses were performed by bilateral 
(-tests using BioEstat 2.0 (Ayres et al. 2000). 
There are divergences in habitat types among 
these species, but we believe they are well suited 
for comparison, as they arc all ground insecti- 
vores, occur in open habitats, and build open to 
domed nests on the ground. 
RESULTS 
We analyzed nests during three breeding 
seasons, 2008 (n = 9). 2009 (n = 8), and 2010 
('> = 15). Nests were domed with a small side 
entrance, often invisible from above. Nests were 
exclusively on the ground, where the grass was 
sufficiently tall to conceal them, usually in slight 
depressions in the soil under dense vegetation 
Fourteen nests were on flat terrain, while 18 were 
in crevices in the banks of the Sorocaba River. 
2-5 m from water. Nest material consisted ot dry 
grasses, and the nest chamber was lined with finer 
grass leaves and grass stems (Fig. I). Nest 
measurements varied (Table 1) and one nest had 
a tubular entrance ~13 cm in length. Males and 
females shared nest building activities with both 
carrying and placing nest materials, often one 
after the other at similar rates (MSF, pers. obs.). 
Adults brought nest materials on average 12.6 ± 
8.4 times/hr (range = 4-24) during 7 hrs of focal 
observation (n = 6 nests). Time gaps between 
visits were 3.6 ± 4.7 min in length (range = 0.1- 
25, n = 88 observations). Two nests found at the 
beginning of construction took 3 days to 
complete. 
The earliest clutch initiation dates (laying of the 
first egg) varied among years: 20 August 2008, 6 
September 2009. and 28 July 2010 (Fig. 2). The 
latest clutch initiation was on 19 October 2008, 
and the latest nesting activity (the last young 
observed in a nest) was on 4 November 2008. 
The average breeding season (pooling the 3 yrs 
together) spanned almost 5 months, but nests 
found in July and November were exceptions 
(only I nest each). Laying initiations were highly 
concentrated in August and September, and the 
average number of active nests was concentrated 
in August through October (Fig. 3). However, 
clutch initiations were clearly concentrated in 
only 1 month (Fig. 2) when each year was 
analyzed separately. 
The basic egg color was pale white and 
markings varied remarkably, even within a single 
nest. Some eggs were predominantly white with 
pale to intense brown spots and blotches moie 
concentrated at the larger end. while others were 
heavily spotted over the entire surtace (Fig. 1). 
Eggs measured 18.2 ± 0.82 mm in length (range 
= 17.1-19.7) and 13.7 ± 0.3 mm in width (range 
= 13,3-14.2), and weighed 1.7 ± 0.12 g (range = 
1 5-2.0) (n = 16). Clutch sizes were two (n = 1), 
three (n = 18). or four (n = 2 ) eggs or young 
(3.05 ± 0 . 4 ), and eggs were invariably laid on 
consecutive days (n = 15 nests). Incubation oi 10 
observed nests, started on the third day after onset 
of laving, even when clutch sizes were two (n — 1 
nest) or four eggs (rt = 1 nest). One egg took 
14 days to hatch, but the incubation period was 
13 days (29 eggs from 10 nests) (13,03 ± 0.2). 
We believe that only females incubated for two 
reasons: ( 1 ) we did not observe adults taking turns 
TABLE 1. Measurements (mm) of Yellowish Pipit nests 
length (OL). inside high (IH), inside diameter (ID), entrance 
(„ = 11 ) : outside high (OH), outside width (OW), outside 
width (EW), and entrance high (EH). 
ow 
OL 
IH 
ID 
EW EH 
Mean ± SD 
Range 
88 ± 8.3 
71-104 
114.4 ± 11.7 130.25 ± 15.6 
93-127.5 104.5-157.3 
62 ± 8 
50.1-74.7 
82.4 ± 16.7 
55.8-108.5 
56 ± 9.9 
37.7-68 
46.5 ± 98.8 
30-58.6 
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