1.1969～1975年に,長野県千曲川の河川敷で,ホオジロの個体間の社会関係と個体の空間的時間的分散様式を,すべての季節にわたって調査し,その社会構造を明らかにした。
2.番いの雌雄には,年間を通じて頻繁な連れ立ち行動がみられ,これが本種の番い維持に大きな役割を果しているものと想定された。1番いは1繁殖期に平均3.0回営巣し,一腹産卵数は平均4.0卵,産卵数に対する巣立率は平均23.0%であった。
3.繁殖期には,雌の行動圏(平均14,580m2)は番い相手の雄(平均19,150m2)にほぼ完全に含まれていた。1繁殖期内では雄は行動圏を移動しないが雌の1/3は,雌が消失した隣接行動圏へ移動し,番いの組みかえが起こった。
4.非繁殖期にも,定住個体は繁殖期とほぼ同一の行動圏へ番いで留まり続けるが,土地をもたない余剰個体がその中に多数存在し,これら未定着個体は未定着状態を続ける限り定住個体に土地の利用を許容されていた。
5.8類型の発声を区別でき,それを発する主体および状況について述べた。特に囀りは,それが発せられる時期によってそれぞれ春•繁殖期•秋の囀りを区別できた。囀りの頻度は一般に独身の方が配偶個体より,新定着個体の方が定住個体よりも高かった。囀りの姿勢は独身と配偶で異なった。
6.ソングポストの最外郭を結んで得られるソングエリアは,隣接個体同士ではほとんど重複しなかった。また隣接個体のソングエリアヘは互いに侵入し合うことも少なかった。
7.攻撃的行動は,威嚇•対峙•追いかけ•身体的闘争の4類型に区別でき,身体的闘争は地上での取っ組み合いと空中闘争に分けられた。争いは1年を通じて1時間に1回内外生起しただけであるが,争いによって他個体を排除する範囲(なわばり)は,ほぼソングエリアと一致していた。このことから,ソングエリアは囀りによって主張されるなわばりであり,その範囲を隣接個体は互いに認識して,避け合っているのであろうと結論した。
8.好適な生息場所は,ほぼ定住番いのなわばりによってモザイク状におおわれているので,若鳥は通常は同性の定住個体が消失した跡地へ定着した。それ以外の若鳥は,定住および新定着雄の秋のなわばり性によって排除されるものと想定された。
9.以上をもとに,小地域的な個体群密度を一定に保つためのなわばりの意義を考察し,スズメ目小鳥類の個体群密度の自己調節について若干論議した。

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Chick feeding^* The growth of nestlings is subject to parents' feeding rate, which is influenced by: 1. chicks' age 2. brood size 3. weather 4. time of day 5. necessary amount and kind of food 6. availability and distribution of food 7. parents' division of labor and sexual difference in feeding, etc. These factors are correlated and work to set the feeding interval and feeding frequency (per hour) which can be observed and recorded for statistical analyses.
Here, these are discussed in relation to chick age and time of the day and are shown by Figs. 10-15, and Tables 8, 9.
Overall feeding rate: In total of observation, the feeding interval ranged from a few minutes to over an hour, in total 3-76 (av. 32.7) min. in the female, 4-104 (av. 40.17) min. in the male and 0-68 (av. 17.95) min. by both sexes. With 3 chicks, the deeding frequency/per hour was 2.08 (0.70/per chick) times in female, 2.01 (0.67/per chick) times in male and 3.68 (1.24/per chick) times by both parents.
Feeding rate by growth of chicks: The female's feeding interval at hatching of chicks is average as long as about 40 minutes (because the naked chicks need to be brooded) and is shortened with the chick growth to about 20 minutes at around 30th day after hatching. But, again the interval is lengthened to about 25-30 minutes. This decrease of feeding rate by the female may support the supposition that by doing so chick's overgrown body weight can be lessened to prepare for flying from the nest (actually the female has been observed to invite the chicks for flying by keeping them hungry).
The feeding frequency also increased from 1.2 times/hour at early period through about 2.7 times/hour at about the age of 30th day and then decreased to about 2.5 times/hour.
In the male, in contrast, the feeding interval at early period was as short as about 25 minutes (as compared with 40 minutes of the female), thus supplementing female's long intervals (by brooding chicks). Then, as the male becomes busy in food search and storage, its feeding interval is extended to average 45 minutes, thus longer and variable than in the female.
But, the combined feeding intervals by male and female are kept constant at the level of between 15-20 minutes intervals, reflecting the sexual behavioral compensation toward a stable feeding rate, adapted to the chick growth of the brood size (in this case 3 chicks). The same is true with the feeding frequency where the male feeds chicks with higher frequency than the female in early nestling period, but later it was kept at lower frequency with higher variaton than in the female, and the female's feeding frequency (though at first lower than in the male) becomes steadily higher toward later nestling period (according to the chick growth) until about 30th day after hatching to be dropped before chicks' flying from nest.
These differences in feeding rate curves by male and female during chicks' growth from hatching to flying, can be more clearly shown by dividing the nestling period into: 1. early (a few days after hatching) 2.middle (between about 10-15 days after hatching) 3. later (between about 16-29 days after hetching) and 4. final (from 30 days after hatching to flying from nest at about 34-36th day) periods (see Fig. 12).
Feeding rate by time of day For this analysis, the activity hours were divided by 2 hour periods from 4.00-6.00 a. m., 6.00-8.00 a. m., 8.00-10.00 a. m., 10.00 a. m. -12.00, 12.00-14.00 p. m., 14.00-16.00 p. m. and 16.00-18.00 p. m., and all the records of feeding intervals (irrespective of nestling age) were tallied by sexes. In this analysis, the mean (M), range (R), standard deviation (σ), variance indices (c₁=σ/M%, c₂=σ/R%) were calculated and shown in Figs.

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